The Age of Radiance (24 page)

We may take the stand that the responsibility for the success of this work has been delegated by the President to Dr. Bush. It has been delegated by Dr. Bush to Dr. Conant. Dr. Conant delegates this responsibility (accompanied by only part of the necessary authority) to Compton. Compton delegates to each of us some particular task, and we can lead a very pleasant life while we do our duty. We live in a pleasant part of a pleasant city [Chicago] in the pleasant company of each other, and have in Dr. Compton the most pleasant “boss” [at the Metallurgical Laboratory] we could wish to have. There is every reason why we should be happy, and since there is a war on, we are even willing to work overtime.

Alternatively, we may take the stand that those who have originated the work on this terrible weapon and those who have materially contributed to its development have, before God and the World, the duty to see to it that it should be ready to be used at the proper time and in the proper way.

I believe that each of us has now to decide where he feels that his responsibility lies.

When the Americans entered the war in December of 1941, Enrico, Laura, and a wide swath of their friends and colleagues were classified as enemy aliens and had to relinquish their binoculars, cameras, and shortwave radios. The Fermis burned their daughter’s Italian second-grade reader (since it was filled with pictures of Mussolini) and had to do something about Giulio, who at the age of five decided to start telling all the neighbors that he hoped the Axis Powers would win. Worried that they might be facing another need to flee with their assets frozen or seized, Enrico withdrew a goodly amount of his Nobel Prize money from the bank, stuffed it in a lead pipe, and buried it in the concrete floor of the basement coal bin in Leonia.

Enrico was especially hurt that, as part of his official wartime status, the post office was reading all his mail. He complained to higher-ups at the postal service and was officially informed that the surveillance had ended. He then opened his mailbox to discover a note to the Leonia carrier ordering that all Fermi mail be opened and reports of its contents submitted. When Enrico complained again, officials said that there was absolutely no order from the Postal Service to read his mail, so the note must be part of a scheme by Axis spies. He burst out laughing.

Since enemy aliens were not permitted to travel by airplane, Enrico now had to regularly commute to the Met Lab in Chicago by rail, always carrying with him an “endorsement of the United States Attorney” letter from the state capital, which enemy aliens needed for any travel. But his work was part of the war effort and top secret—he traveled under the name Eugene Farmer—so he wasn’t able to tell state officials in Trenton exactly why he needed to constantly go to Chicago (not until October 12, 1942, Columbus Day, did the US government declare that Italians were no longer enemy aliens, and on July 11, 1944, after completing the required five years of residence, Enrico and Laura Fermi were sworn in as American citizens). In April 1941, Arthur Compton decided that he needed Fermi in Chicago full-time, so the family left New Jersey and found a nice rental close to the U of C campus. Unfortunately, the apartment came with a lavish radio that included a shortwave band, and the building’s other renters were two Japanese American girls. The radio manufacturer sent a serviceman to disable the feature, but it was against the law for so many enemy aliens to be living together, and the girls were forced to leave.

By July 1942, Fermi and Szilard had enough data from their experimental piles to try to design one that could go critical—chain-react. Wally Zinn’s designs for the uranium oxide cores were pressed into dies, with 250 tons of graphite and 6 tons of uranium cut by hand. They still needed more information on how to control the chain, and what the size of a critical pile would be, and would go through thirty piles at this intermediate stage before they were ready to birth the forge both of nuclear power and nuclear weapons.

H
istory’s first atomic power-generating nuclear reactor was to have been built in a facility in the Argonne Forest, which Arthur and Betty Compton had come across while out horseback riding. But when the contractor, Stone & Webster, suffered a strike, delaying construction, Fermi talked Compton into building the pile right on the University of Chicago campus. He insisted that he knew how to stop the reaction before what in time would be called a meltdown could destroy the city in an atomic conflagration.

The first pile’s location was odd in another way. University of Chicago president Robert Hutchins had decided in 1939 that football was a distraction from higher education and canceled it. Twenty-two years later, after football returned to the University of Chicago, its students created a unique cheer:

Cosine, secant, tangent, sine,

3.14159.

Square root, cube root, BTU,

Sequence, series, limits too.

Rah.

But in that autumn of 1942 when Fermi was looking for his great pile’s location, Chicago’s campus football stadium, Stagg Field, in the style of a faux–English Gothic castle, with ivy-bedecked stucco turrets, battlements, a keeplike bell tower, and gargoyles, had been abandoned, its field now weedy and returning to the wild. Underneath the building’s eaves was a little-used squash court, sixty feet long, thirty feet wide, and twenty-six feet high, with slate walls. It was perfect.

Construction began November 16, 1942, on CP-1—Chicago Pile-1—the most dangerous scientific experiment in American history. A team of high school dropout toughs waiting on their draft notices were recruited to set 771,000 pounds of pure graphite bricks in a lattice array with 2.25-inch uranium cores (80,590 pounds of oxide and 12,400 pounds of metal). The reactor would grow into an oval shape, twenty-five feet wide and twenty feet high, controlled by rods coated in cadmium. The graphite slowed the neutrons enough so that they would more efficiently hit their nuclei, freeing more neutrons, while the cadmium absorbed enough of the free neutrons to slow their barrage and quiet the pile.

Nuclear scientists had never seen an atom, much less a nucleus, the object of their profound fascination; all of their experiments, and their resulting theories, arrived secondhand, through the response of instruments. Fermi was reading
Winnie-the-Pooh
to improve his English, so his CP-1 instruments were given names of characters in the
Pooh
stories—Tigger, Piglet, Kanga, and Roo. In this case, measurements would be taken with a boron trifluoride counter that clicked just like a Geiger. When the first pile chain reacted and went critical, however, the counters would make a noise like nothing these physicists had ever heard before.

The graphite bricks were machined in the West Stands, overseen by millwright August Knuth. Physicist Albert Wattenberg:
“We found out how coal miners feel. After eight hours of machining graphite, we looked as if we were made up for a minstrel. One shower would remove only the surface graphite dust. About a half-hour after the first shower the dust in the pores of your skin would start oozing. Walking around the room where we cut the graphite was like walking on a dance floor. Graphite is a dry lubricant, you
know, and the cement floor covered with graphite dust was slippery.” Fermi, stripped to the waist, was black and glistening. One colleague remarked that he could have played Othello. . . . In the late afternoon as the sun faded, the squash court was so filled with a smog of black dust that the scientists and the workers could only be seen by the whites of their teeth and their eyes.

Herb Anderson:
“For the construction of the pile Fermi assigned the responsibility jointly to [Walter] Zinn and me. Our two groups combined for a concerted effort. Two special crews were organized: one machined the graphite, the other pressed the uranium oxide powder using specially made dies in a large hydraulic press. Both crews managed to keep their output up to the rate of the deliveries. Thus in our report for the month ending October 15, Zinn and I could state that 210 tons of graphite had been machined. . . . We organized into two shifts: Wally Zinn took the day shift, mine was the night shift. A simple design for a control rod was developed which could be made on the spot: cadmium sheet nailed to a flat wood strip was inserted in a slot machined in the graphite for this purpose. One special, particularly simple, control rod was built by Zinn; it operated by gravity through weights and a pulley and was called ‘Zip.’ It was to be pulled out before the pile went into operation and held by hand [Zinn’s] with the rope. In case of an emergency or if Zinn collapsed, the rope would be released and Zip would be drawn into the pile by gravity.”

Day after day, the pile grew. Fermi protégé Leona Woods—twenty-three years old, and the only woman on the project—took careful measurements. As the finish line drew nigh, the tension in the room grew along with the tonnage of graphite and uranium. Everyone who worked in the squash court knew this would be it. But, what if it wasn’t . . . or what if something dreadful happened? In Washington, their bosses had already gone forward as though Fermi and Szilard would succeed perfectly in this revolutionary endeavor, having contracted with DuPont to build a $350 million nuclear reactor based on Fermi’s design on the Columbia River outside Pasco, Washington.

There was more than meltdown to fear. Al Wattenberg:
“One aspect of Fermi that wasn’t so fortunate for me was that he was also my chauffeur. I would drive the car over to his house twice a week for a year and a half or so. Sometimes we picked up Leona and we would drive out to work together. And we kept talking about doing estimates of things—he was constantly estimating things. I tend to be an unbeliever in his intuition. It was that he had calculated things, and he remembered what he’d calculated. These little tiny estimates of things—he was always doing it, and he remembered them. Anyway, one of the days we were at a railroad crossing, and he was the driver.
I forget what we were calculating in our heads at the time, but anyway, the train went by and, of course, we went ahead because we have the calculation on our minds. It was two tracks, not one, and we almost got hit by the train coming in the other direction—missed by three seconds. And I don’t know whether he was jocular about his fatalism or not, but he said, ‘You see? It is exceedingly important that you always be with me when I drive.’ ”

Fermi had to create an environment that would focus the neutrons onto their atomic targets until they struck regularly enough to initiate a continuously explosive cascade of splintering nuclei. He tried submerging the pile in water, enclosing it in metal and vacuuming out the air, but none of these were helpful. Emilio Segrè:
“The pile, according to plan, was shaped as a rotational ellipsoid with a polar radius of 309 centimeters and an equatorial radius of 388 centimeters. Most of the uranium lumps had to be placed in the central region for better utilization. The weight of the uranium was approximately six tons. To use the material efficiently the purest fuel had to be located more centrally and one had to watch carefully the details of the geometry because they could affect the reproduction factor. The whole structure was supported by a wooden frame. Fermi feared that there might not be enough material to reach criticality, and to reduce parasitic neutron absorption by the nitrogen of the air, he ordered a huge rubber balloon to enclose the pile.” Anderson’s request for an enormous square balloon from Goodyear Tire & Rubber led to a great deal of joking since the aerodynamics of a square balloon are poor, and Goodyear wasn’t told of its purpose. Experiments in the final stages indicated that the last layer of uranium and graphite didn’t need to be laid, and that the balloon didn’t need to be sealed.

Physicist Harold Agnew:
“Graphite was an awful material; it’s heavy, and dense, and very slippery. Those things are heavy, and you could really get your fingers pinched and also hurt your knees because you had to crawl on this pile of graphite. . . . All during this time, it was very precise, we always stopped for lunch, and we had a sort of a team of us who always went to lunch together at the Commons, and we talked about things. Not about work things, but I remember one thing that really impressed me was our fear of where the Germans were. This was a real thing that maybe every third lunch would come up. Where do we think we are, where do we think they are; it was a concern during those days.”

On the early afternoon of December 1, tests indicated that critical size was approaching. At 4:00 p.m., Zinn’s group was relieved, and Anderson’s
stepped in. Then, the fifty-seventh layer of graphite and uranium bricks was set in place. So exact were Fermi’s calculations, based on the ever-growing pile, that Enrico had already predicted to the exact brick the point at which the reactor would become self-sustaining, and he made the graduate student promise this would not be a repeat of the success of the fission experiment back at Columbia, which only Anderson and Dunning had witnessed. Zinn joined Anderson to measure the activity; they were both convinced that, when the cadmium rods were fully removed, the pile would chain-react and split its own nuclei until its atomic energies were exhausted. Anderson and Zinn had the control rods locked and the workers had the rest of the day off. Anderson:
“It was a great temptation for me to pull the final cadmium strip and be the first to make a pile chain react. But Fermi had anticipated this possibility. He had made me promise that I would make the measurement, record the result, lock them all in place, go to bed, and nothing more.”