The Making of the Atomic Bomb

Bush changed his mind within days. Groves immediately tackled his worst problems and solved them.

One of the first issues the heavyweight colonel had raised with Nichols was ore supply: was there sufficient uranium on hand? Nichols told him about a recent and fortuitous discovery: some 1,250 tons of extraordinarily rich pitchblende — it was 65 percent uranium oxide — that the Union Miniere had shipped to the United States in 1940 from its Shinkolobwe mine in the Belgian Congo to remove it beyond German reach. Fr6d6ric Joliot and Henry Tizard had independently warned the Belgians of the German danger in 1939. The ore was stored in the open in two thousand steel drums at Port Richmond on Staten Island. The Belgians had been trying for six months to alert the U.S. government to its presence. On Friday, September 18, Groves sent Nichols to New York to buy it.

On Saturday Groves drafted a letter in the name of Donald Nelson, the civilian head of the War Production Board, assigning a first-priority AAA rating to the Manhattan Engineer District. Groves personally carried the letter to Nelson. “His reaction was completely negative; however, he quickly reversed himself when I said that I would have to recommend to the President that the project should be abandoned because the War Production Board was unwilling to co-operate with his wishes.” Groves was bluffing but it was not the bluster that swayed Nelson; he had probably heard by then from Bush and Henry Stimson. He signed the letter. “We had no major priority difficulties,” notes Groves, “for nearly a year.”

The same day Groves approved a directive that had been languishing on his predecessor's desk throughout the summer for the acquisition of 52,000 acres of land along the Clinch River in eastern Tennessee. Site X, the Met Lab called it. District Engineer Marshall had thought to wait to buy the land at least until the chain reaction was proved.

On September 23, the following Wednesday, Groves' promotion to brigadier came through. He hardly had time to pin on his stars before attending a command performance in the office of the Secretary of War called to assemble Bush's outmaneuvered Military Policy Committee with Stimson, Army Chief of Staff George Marshall, Bush, Conant, Somervell, Styer and an admiral on hand. Groves described how he intended to operate. Stimson proposed a nine-man committee to supervise. Groves held out for a more workable three and won his point. Discussion continued. Abruptly Groves asked to be excused: he needed to catch a train to Tennessee, he explained, to inspect Site X. The startled Secretary of War agreed and Leslie Richard Groves, the new broom that would sweep the Manhattan Engineer District clean, departed for Union Station. “You made me look like a million dollars,” Somervell praised Groves when he got back to Washington. “I'd told them that if you were put in charge, things would really start moving.” They did.

Enrico Fermi began planning a full-scale chain-reacting pile in May 1942 when one of the exponential piles his team built in the west stands of Stagg Field indicated its k at infinity would muster 0.995. The Met Lab was searching out higher-quality graphite and sponsoring production of pure uranium metal, denser than oxide; those and other improvements should push k above 1.0. “I remember I talked about the experiment on the Indiana dunes,” Fermi told his wife after the war, “and it was the first time I saw the dunes… I liked the dunes: it was a clear day, with no fog to dim colors… We came out of the water, and we walked along the beach.”

As they began preparations that summer Leona Woods remembers swimming “in frigid Lake Michigan every afternoon at five o'clock, off the huge breakwater rocks at the 55th street promontory” — she, Herbert Anderson, Fermi. She was still a graduate student, twenty-two and shy. “One evening, Enrico gave a party, inviting Edward and [Mici] Teller, Helen and Robert Mulliken (my research professor), and Herb Anderson, John Marshall, and me.” They played Murder, the parlor game then in fashion. “The second the lights went out on this particular evening, I shrank into a corner and listened with astonishment to these brilliant, accomplished, famous sophisticated people shrieking and poking and kissing each other in the dark like little kids.” All nice people are shy, Fermi consoled her when he knew her better; he had always been dominated by shyness. She records his sly self-mockery: “As he frequently said, he was amazed when he thought how modest he was.”

Woods was finishing her thesis work during the summer but sometimes helped Anderson scour Chicago for lumber. CP-1 — Chicago Pile Number One — Fermi planned to build in the form of a sphere, the most efficient shape to maximize k. Since the pile's layers of graphite bricks would enlarge concentrically up to its equator, they would need external support, and wood framing was light and easy to shape and assemble. “I was the buyer for a lot of lumber,” Anderson says. “I remember the Sterling Lumber Company, how amazed they were by the orders I gave them, all with double X priority. But they delivered the lumber with no questions asked. There was almost no constraint on money and priority to get what we wanted.”

Horseback riding one Saturday afternoon in the Cook County Forest Preserve twenty miles southwest of Chicago, Arthur and Betty Compton found an isolated, scenic site for the pile building, a terminal moraine forested with hawthorne and scrub oak known as the Argonne Forest. The Army's Nichols negotiated with the county to use the land; Stone & Webster began planning construction.

The Fermis rented a house from a businessman moving to Washington for war work; since they were enemy aliens and not allowed to own a shortwave radio the man had to have his big all-band Capehart temporarily disabled of its long-distance frequencies, though it continued to supply dance music to the party room on the third floor. Fermi was angry to find his mail being opened and complained indignantly until the practice was stopped (or managed more surreptitiously). The Comptons gave a series of parties to welcome newcomers to the Met Lab. “At each of these parties,” Laura Fermi writes, “the English film Next of Kin was shown. It depicted in dark tones the consequences of negligence and carelessness. A briefcase laid down on the floor in a public place is stolen by a spy. English military plans become known to the enemy. Bombardments, destruction of civilian homes, and an unnecessarily high toll of lives on the fighting front are the result… Willingly we accepted the hint and confined our social activities to the group of ‘metallurgists.’” Compton, who describes himself as “one of those who must talk over important problems with his wife,” arranged uniquely to have Betty Compton cleared. None of the other wives was supposed to know about her husband's work. Laura Fermi found out, like many others, only at the end of the war.

In mid-August Fermi's group could report a probable k for a graphite-uranium oxide pile of “close to 1.04.” They were working on control-rod design and testing the vacuum properties of both metal sheet and balloon cloth. The cloth was Anderson's idea, a possible alternative to canning the pile to exclude neutron-absorbing air. It proved serviceable and Anderson followed up: “For the balloon cloth enclosure I went to the Goodyear Rubber Company in Akron, Ohio. The company had a good deal of experience in building blimps and rubber rafts but a square balloon 25' on a side seemed a bit odd to them.” They made it anyway, “with no questions asked.” It should be good for a 1 percent improvement in k.

Between September 15 and November 15 Anderson, Walter Zinn and their crews also built sixteen successive exponential piles in the Stagg Field west stands to measure the purity of the various shipments of graphite, uranium oxide and metal they had begun to receive in quantity. Not all the uranium was acceptable. But Mallinckrodt Chemical Works in St. Louis, specialists at handling the ether necessary for oxide extraction, began producing highly purified brown oxide at the rate of thirty tons a month, and the National Carbon Company and a smaller supplier, by using purified petroleum coke for raw material and doubling furnace time, significantly improved graphite supplies (graphite is molded as coke, then baked in a high-temperature electric-arc oven for long hours until it crystallizes and its impurities vaporize away). By September regular deliveries began to arrive in covered trucks. Physicists doubled as laborers to unload the bricks and cans and pass them into the west stands for finishing.

Walter Zinn took charge of preparing the materials for the pile. The graphite came in from various manufacturers as rough 4Vi by 4¹/4-inch bars in 17- to 50-inch lengths. So that the bars would fit closely together they had to be smoothed and cut to standard 16'/2-inch lengths. About a fourth of them also had to be drilled for the lumps of uranium they would hold. A few required slots machined through to make channels for control rods. The uranium oxide needed to be compressed into what the physicists called “pseudospheres” — stubby cylinders with round-shouldered ends — for which purpose the press from the Jersey City junkyard had been shipped to Chicago the previous winter.

For crew Zinn had half a dozen young physicists, a thoroughly able carpenter and some thirty high school dropouts earning pocket money until their draft notices came through. They were Back of the Yards boys from the tough neighborhood beyond the Chicago stockyards and Zinn improved the fluency of his swearing keeping them in line.

Machining the graphite was like sharpening thousands of giant pencils. Zinn used power woodworking tools. A jointer first made two sides of each graphite brick perpendicular and smooth; a planer finished the other two