How the nuclear age burst onto the world from a squash court
On Road Trip 2013, CNET's Daniel Terdiman traveled to the Argonne National Lab to find out the history of the world's first nuclear reaction, Chicago Pile-1.
LEMONT, Ill. -- On December 2, 1942, one of the most important moments in world history took place on a squash court underneath the bleachers of the University of Chicago's football field.
While the location may seem as mundane as possible, the event was anything but. That day, with many of the world's most accomplished physicists on hand, Nobel Prize winner Enrico Fermi successfully completed the first-ever sustained chain reaction.
A crucial piece in the race to create weapons-grade plutonium for a future atomic bomb, the experiment proved that man had some power over nuclear energy. And the world would never be the same. As part of Road Trip 2013, I went to Chicago to learn about this crucial history.
Although the project, known as Chicago Pile-1, produced only enough power to light a bulb, it was momentous. As a document (PDF) hosted on the U.S. Department of Energy's Web site describes it, "man had unleashed and controlled the energy of the atom." But for years, almost no one knew about what happened that December day underneath the Stagg Field bleachers. The project was top secret, its participants sworn to secrecy, and the evidence was quickly dismantled. No known photographs were taken. Only the signatures of many of the 49 people in the room on a bottle of Chianti given to Fermi attest to the fact that CP-1, as it was known, even happened.
But of course, it did happen. CP-1 was conducted under the auspices of what was known as the Metallurgical Laboratory -- a precursor to the Argonne National Laboratory, the United States' first science and engineering research national lab -- and its work carried on immediately. As soon as CP-1's sustained chain reaction was completed, the project was taken apart and quickly re-assembled in the Argonne Woods in Lemont, a suburb of Chicago. A working replica of CP-1, built at "Site A," continued Fermi's work. And the rest is history.
Today, all that's left of the original CP-1 is a monument on the University of Chicago campus. There, a plaque declares, "On December 2, 1942, man achieved here the first self-sustaining chain reaction and thereby initiated the controlled release of nuclear energy."
CP-1
For all its historical significance, CP-1 was itself probably not all that impressive to look at. Shaped like a lattice structure and built on a wooden frame on the squash court in just about a month, the pile was made of alternate layers of graphite, which contained uranium metal and/or oxide, and which were separated by layers of solid graphite blocks. According to the Department of Energy document, the pile was 19 feet high, and 24 feet wide by 24 feet long. It contained 385.5 tons of graphite, and 46.5 tons of uranium metal and oxides, according to the document.
Fermi and his team were meticulous. Fermi himself had the world's best combined physics and mathematics skills, according to Argonne National Lab nuclear engineer Roger Blomquist, and he didn't count on the sustained chain reaction simply happening as planned without doing his homework. Over the course of weeks before the final experiment, he and his colleagues conducted about 30 subcritical experiments, Blomquist said, allowing Fermi to be almost exact in his prediction several days earlier of how many of the graphite blocks it would take in order to successfully go critical.
CP-1 was built to resemble a sphere, the optimal shape in terms of surface-to-volume ratio, Blomquist explained, given that that would minimize the leakage of neutrons from the core.
On December 2, all was ready. A neutron-absorbing control rod made of indium, cadmium, and silver that had been inserted into the core was removed, and the chain reaction began. Almost immediately Fermi's theories were proven correct, but in order to ensure that no one would question his result, he decided to let the chain reaction go on. For 18 minutes, it proceeded, until at 2:53 p.m. Fermi ordered the control rod re-inserted, and the reaction stopped.
Of course, Fermi had not been unaware of possible dangers of starting a self-sustaining chain reaction, Blomquist said, and had readied multiple safeguards. The first was a man who stood against the railing alongside the gallery where the scientists watched holding onto a rope, which kept a control rod from entering the core. In an emergency, that rope was to be cut, which would have quickly re-inserted it, absorbing neutrons in the core, and slowing down the reaction. A second safeguard was a number of buckets of cadmium in liquid form that could be quickly poured onto the top of the pile, where it would leak into the core and shut down the reaction.
But Fermi was successful, and CP-1 carried the day.
Today, CP-1's legacy continues. Blomquist said that all new nuclear reactors are brought on line using the same series of sub-critical experiments that Fermi employed. And at Argonne National Lab, a legacy of nuclear research has led to science that seeks to prove that nuclear power is not only efficient and inexpensive relative to fossil fuels, but safe.
As Blomquist put it, the nuclear energy field knows it has terrible PR, especially thanks to disasters like Three Mile Island, Chernobyl, and Fukushima. Yet they continue their work, arguing to the world that there is no safer way to efficiently power the planet, and that it is nuclear weapons research that leads to commercial use, rather than the opposite.