Chicago Pile-1

Experiment paved the way for nuclear science and a Lab in Los Alamos.

By Brye Steeves | August 29, 2022

Chicago Opt
Artist Leo Vartanian used ink made of graphite from the Chicago Pile-1 experiment. The four prominently featured scientists are, from left, Leo Szilard, Arthur Compton, Enrico Fermi, and Eugene Wigner. Only 43 prints of the original lithograph were made; one is on display in the National Security Research Center, which is the Lab’s classified library.

Eighty years ago on a bitter-cold December day in 1942, scientists gathered at an abandoned squash court at the University of Chicago where they would ultimately enable a secret lab in Los Alamos to change the world.

Enrico Fermi oversaw the Chicago Pile-1 experiment that created the world’s first self-sustaining nuclear reactor. This led to the creation of the atomic bomb at the Los Alamos Lab, where Fermi continued his work.

The group, led by Italian physicist and Nobel laureate Enrico Fermi, stacked graphite bricks, piling 57 layers that totaled more than 770,000 pounds. Later named Chicago Pile-1, their goal was to create the world's first self-sustaining, controlled nuclear chain reaction.

Inside the approximately 20-foot-tall pile were smaller blocks of uranium and control rods that, when removed, would cause the reaction to go critical  meaning it would create a nuclear chain reaction. It was roughly $1 million worth of materials, equivalent to nearly $16 million today, and reinforced the concept that a nuclear chain reaction would allow the weaponization of the atom.

"Its success would be the crucial proof needed to know it would be possible to create an atomic bomb," said LANL historian Roger Meade. "This was the precursor to the lab we have today."

But no Eeyore

Fermi watched alongside his team all men and just one woman, 23-year-old physicist Leona Marshall  from a balcony. They were monitoring the experiment on instruments named after fictional children's storybook characters: Pooh, Piglet, And Tigger, according to the department of energy.

Around 3:30 p.m. , rods were removed. One was controlled from a balcony, one was an emergency safety rod, and another would be withdrawn to cause criticality.

"Although Fermi was confident that he could control his experiment," Meade said, "he nonetheless stationed three graduate students, known as the suicide squad, on top of the reactor to pour buckets of a cadmium solution over the experiment if the safety mechanism failed. The cadmium (a chemical element) solution would soak up neutrons and quash the fission process."

Luckily for the students, the reactor worked as planned. As the final rod came out, Fermi reportedly said, "This is going to do it. Now it will become self-sustaining."

He was right.

Chicago Img2@2x
Members of the Chicago Pile-1 team met on the experiment’s fourth anniversary in 1946. Future Los Alamos Director Harold Agnew is on the far left of the middle row; the experiment’s only female physicist Leona Marshall is to the right of center; Nobel Laureate Enrico Fermi is on the far left of the first row.

On to Los Alamos

A coded message, "The Italian navigator has just landed in the new world," notified government officials of the experiment's success and the team celebrated with paper cups of Chianti, an Italian red wine. Members of the team signed the label on the wine bottle, which ended up being the only written record of attendees, according to the Department of Energy.

Many of the 43 scientists from the Chicago pile-1 team, including Fermi, would go on to work for the Manhattan projects secret wartime lab in Los Alamos. There, the results of the experiment were used to develop the world's first nuclear explosive devices. First, during the Trinity test in July 1945, followed by the two atomic bombs that were released weeks later in combat against Japan. World War II ended shortly thereafter.  🔎