Chapter 1: The Manhattan Project and the Met Lab

The Metallurgical Laboratory at the University of Chicago, commonly known as the “Met Lab,” was integral to the Manhattan Project. Its primary mission was to devise a feasible method for producing plutonium. Starting in 1939, a dedicated group of scientists, including Enrico Fermi, Leo Szilard, Walter Zinn, and Herbert Anderson, conducted experiments at Columbia University with chain-reacting nuclear “piles” to measure neutron emissions from fission processes. By February 1942, the project moved to the Met Lab with the aim of achieving a self-sustaining nuclear reaction, which would serve as a blueprint for large-scale plutonium production.

In a previously unused racquetball court beneath Stagg Field on the University of Chicago campus, researchers selected this location for their experiment, assured by Fermi that the chances of an accident were minimal. Despite this assurance, the scientists remained unsure about controlling the reaction. When asked about potential failures, Fermi humorously replied, “I will leave — relaxed.”

In frigid conditions, teams of workers and researchers constructed the pile by stacking layers of graphite blocks atop a rudimentary wooden frame. The bars had to be meticulously cut to fit snugly together, with some drilled to accommodate uranium pieces and others designed to hold 14-foot cadmium “control rods.” These rods, when removed, would push the reaction into a critical state.

The construction concluded on December 1, 1942, utilizing 771,000 pounds of graphite, alongside 80,590 pounds of uranium oxide and 12,400 pounds of uranium metal—materials valued at approximately $1 million.

On December 2, 1942, Fermi and his team observed from a balcony as the last researcher on the floor, George Weil, cautiously removed the cadmium rods per Fermi’s instructions. These rods absorbed neutrons, acting as a brake on the nuclear reaction. Equipped with Geiger counters, the scientists closely monitored the k value of the reaction—the effective neutron multiplication factor, indicating how many neutrons from fission would instigate further fission events. A sufficiently high k value would confirm the reaction's ability to sustain itself.

After a brief pause, Fermi instructed Weil to pull the final cadmium rod an additional 12 inches. He confidently told Arthur Holly Compton, “This will make it happen. Now it will become self-sustaining.” Indeed, the pile reached a critical state, marking the onset of the world’s first self-sustaining chain reaction. It recorded a k value of 1.0006 and achieved a thermal output of 0.5 watts (eventually operating at a maximum of 200 watts). Physicist Herbert Anderson recounted:

“At first, you could hear the neutron counter clicking softly. Then the clicks accelerated and merged into a roar; the counter could no longer keep pace. It was then that we switched to the chart recorder. However, as we made that change, a profound silence filled the room while we observed the rapid rise of the pen on the recorder. Everyone understood the significance of that moment; we were in the critical system, and the counters couldn't cope any longer. Fermi raised his hand and announced, ‘The pile has gone critical.’ There was no doubt among those present.”

Less than five minutes later, Fermi ordered the reactor to be dialed back. Eugene Wigner opened a bottle of Bertolli Chianti he had been saving for such a celebration. The team toasted with paper cups, later signing the straw wrapper from the bottle. A total of 49 scientists and workers witnessed this historical moment.

A few hours later, Arthur Compton, the head of the Met Lab, contacted his superior at Harvard, James Conant, saying, “Jim, you’ll be interested to know that Fermi has just arrived in the ‘New World.’”

The first video, "Argonne nuclear pioneers: Chicago Pile 1," provides insights into the groundbreaking achievements of the scientists involved in this monumental project.

Chapter 2: The Evolution of Nuclear Reactor Technology

The second video, "How Was the First Nuclear Reactor Developed? (Chicago Pile 1)," explores the development process and the challenges faced in creating the first nuclear reactor.