Chapter 1: A Strange Experiment in Suburbia

In 1995, a quiet neighborhood in Detroit witnessed a remarkable event that residents would remember for years. Government agents, some dressed as if preparing for a space mission, descended upon a seemingly ordinary house. They meticulously dismantled a shed in the backyard, placing the disassembled parts into sealed containers marked with radioactive warnings. While the agency claimed to be the EPA responding to a spill, the reality was far more shocking—they were dismantling a makeshift nuclear reactor created by a 17-year-old named David Hahn.

The teenager had constructed the device from various components he scavenged. His self-made Geiger counter had registered dangerously high levels, prompting him to alert local authorities. This alarming story, reminiscent of a reckless scientific endeavor, echoes the history of the first chain reaction, which also occurred in a highly populated area—specifically, beneath a football stadium in Chicago. Unlike Hahn’s case, however, the government supported this groundbreaking initiative and celebrated the scientists involved. The lead scientist, Enrico Fermi, became a prominent figure in the atomic age.

Section 1.1: The Birth of Chicago Pile-1

During World War II, both the Allied and Axis powers raced to develop atomic bombs. Before the destructive weapons could be created, however, a fundamental breakthrough was necessary: the demonstration of a self-sustaining nuclear chain reaction. This pivotal moment occurred at Chicago Pile-1 (CP-1). Louise Lerner from the University of Chicago explains, "A nuclear reactor functions by splitting atoms. Certain elements, like uranium, emit neutrons over time. A reactor is designed to arrange uranium in a way that encourages these neutrons to collide with other uranium atoms, causing them to split and release more neutrons, which continues the process—hence the term 'chain reaction.'"

Throughout WWII, multiple research facilities were focused on this project as part of the Manhattan Project, ultimately consolidating their efforts at the University of Chicago. The reactor was constructed in a squash court beneath the abandoned Stagg Field, where the university's football team had ceased operations years earlier. Arthur Compton, head of the Metallurgical Laboratory, selected this location after encountering challenges in finding a safer, more remote site.

Richard Rhodes, in his book "The Making of the Atomic Bomb," notes that Compton kept the project secret from the university president and the mayor of Chicago. "The term meltdown had yet to enter the reactor engineer's vocabulary—Fermi was pioneering this field—but Compton was risking a small-scale disaster in a crowded urban setting. Fortunately, Fermi was an exceptionally skilled engineer."

Fermi assured Compton that there was a "delayed neutron response during fission," providing a window for control with specialized rods.

Subsection 1.1.1: The Reactor's Structure

The Chicago Pile's design was surprisingly simple. As described by Alex Wellerstein in The New Yorker, it consisted of "a stack of forty thousand graphite blocks, arranged in a wooden frame, measuring twenty-five feet across and twenty feet tall. Within this structure, half of the blocks contained small amounts of uranium oxide, with a few housing refined uranium metal, a relatively new production technique. The reactor lacked numerous safety features."

Despite its rudimentary appearance, constructing the Pile required extensive calculations and numerous attempts, which totaled around thirty. The final configuration was completed on December 1, 1942, incorporating approximately:

• 800,000 pounds of graphite
• 80,000 pounds of uranium oxide
• 12,000 pounds of uranium metal

At the time, the total cost of the project neared one million dollars. Fermi designed the Pile with fifty-seven layers, ensuring the "k" value exceeded one, indicating the potential for self-sustained reactions.

While safety measures were limited, the design included methods for controlling the reaction. Certain areas of the Pile had openings through which fourteen-foot control rods made of cadmium could be adjusted, thereby regulating the neutron activity. Rhodes notes that at least one rod was operated manually, with a physicist making incremental adjustments as directed by Fermi. The reactor also had three emergency control systems, including one that could be activated by a solenoid if neutron levels exceeded safe thresholds.

Chapter 2: A Historic Achievement

The day following the completion of the Pile, Fermi expressed confidence that it could achieve the desired chain reaction. On the morning of December 2, Fermi instructed an assistant to gradually extract the manual control rod. Above the squash court, a team of physicists monitored the "k" value using instruments affectionately named Pooh, Piglet, and Tigger. As the value approached one, an unexpected loud bang interrupted the tension—one of the containment rods had been triggered.

With the goal in sight, Fermi nonchalantly sent the team out for lunch, resembling a typical faculty gathering rather than a group on the verge of scientific breakthrough. After their meal, the team resumed their work, and shortly after 3:30 PM, the "k" value surpassed one. Fermi decided to terminate the experiment moments later, successfully creating the first artificial chain reaction with a device that, while rudimentary, marked a monumental achievement in scientific history.

While the initial output was only about half a watt, the potential for a million watts within ninety minutes loomed ominously over Chicago.