Walter Henry Zinn led the team that designed the first ever nuclear power reactor that generated enough energy to power four 200-watt light bulbs today in 1951. Now WE know em


Walter Henry Zinn was born December 10, 1906 in Kitchener, Ontario, Canada.

Walter graduated from Queen’s University with a mathematics degree, and went on to earn his Ph.D. in nuclear physics at Columbia University in 1934.

Walter Zinn is credited with starting the world’s first self-sustaining nuclear reaction by withdrawing a control rod from the world’s first nuclear reactor on December 2, 1942 at the University of Chicago Metallurgical laboratory.


Walter Zinn (standing) presses a button to shut down the Chicago Pile-3 research reactor

Walter Zinn (standing) presses a button to shut down the Chicago Pile-3 research reactor

During World War II, Walter Zinn worked on the Manhattan Project.

After his work helping to develop the Atom Bomb, he became the director of the Argonne National Laboratory in 1946.

National Reactor Testing Station

The National Reactor Testing Station was established in 1949 on an 890 square-mile desert complex about 18 miles southeast of Arco, Idaho.

A team led by Walter Zinn, was tapped to design the “Experimental Breeder” nuclear reactor.


Installation of “Experimental Breeder Reactor 1” began early in 1951, initially referred to as “Chicago Pile 4” or “Zinn’s Infernal Pile.”


Experimental Breeder Reactor 1 (EBR-1)was completed on August 24, 1951.

December 20, 1951

For the first time, atomic energy successfully produced enough electricity to power four 200-watt light bulbs on December 20, 1951.


December 20, 1951, when four light bulbs were lit with electricity generated from the EBR-1 reactor.

December 20, 1951, when four light bulbs were lit with electricity generated from the EBR-1 reactor.

The following day, the nuclear reactor harvested enough electricity to light the whole building, producing 200kW of electricity out of 1.4MW of heat generated by the reactor.


Experimental Breeder Reactor 1 (EBR-1)

Experimental Breeder Reactor 1 (EBR-1)

However, the purpose of EBR-1 had not been to produce electricity, but rather to validate Enrico Fermi’s nuclear physics theory which suggested that a breeder reactor should be able to produce more fuel atoms than the reactor consumed.

By 1953, along with generating electricity, experiments revealed the EBR-1 reactor was producing enough additional fuel during fission to confirm Fermi’s hypothesis.

Then in 1955, Walter Zinn was elected as the first president of the American Nuclear Society.

However, on November 29, 1955, Zinn’s reactor at EBR-I suffered a partial meltdown during a coolant flow test. The flow test was trying to determine the cause of unexpected reactor responses to changes in coolant flow. It was subsequently repaired for further experiments, which determined that thermal expansion of the fuel rods and the thick plates supporting the fuel rods was the cause of the unexpected reactor response.

Although EBR-I produced the first electricity available in-house, a nearby reactor plant called BORAX-III was connected to external loads, powering the nearby city of Arco, Idaho in 1955, the first time a city had been powered solely by nuclear power.

Besides generating the world’s first electricity from atomic energy, EBR-1 was also the world’s first breeder reactor and the first to use plutonium fuel to generate electricity.

Then EBR-1 was deactivated in 1964 and replaced with a new reactor, EBR-II. Landmark status for EBR-I was granted by President Lyndon Johnson and Glenn T. Seaborg on August 25, 1966.

EBR-1 was declared a National Historic Landmark in 1965 and an IEEE Milestone in 2004.

The site has been open to the public since 1976, but is only open between Memorial Day and Labor Day.

Also on display at the site are two prototype reactors from the Aircraft Nuclear Propulsion Project of the 1950s.

Walter Henry Zinn died February 14, 2000 in Clearwater, Florida at the age of 93.

Now WE know em


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