December 2, 1942: The Graphite Piles Up

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“The Italian navigator has landed in the New World.”

“How were the natives?”

“Very friendly.”

With these code words, Arthur Compton, head of the Metallurgical Laboratory at the University of Chicago, notified James Conant, chair of the National Defense Research Committee (overseeing the Manhattan Project), that the world’s first successful, man-made, self-sustaining chain reaction had taken place, in a squash court beneath the viewing stands at Stagg Field, University of Chicago.

Other observers were a bit more loquacious:

“Nothing very spectacular had happened.  Nothing had moved, and the pile itself had given no sound. . .. We had known that we were about to unlock a giant; still, we could not escape an eerie feeling when we knew we had actually done it.  We felt as, I presume, everyone feels who has done something that he knows will have very far-reaching consequences which he cannot foresee.”

With the discovery of nuclear fission by German scientists Otto Hahn and Fritz Strassmann, as explained and named by their collaborators Lise Meitner and Otto Frisch, it was known that the possibility of creating a self-sustaining chain reaction was possible.  However, finding the right material—one that would produce more splitting neutrons than it absorbed, and the right moderating material, to control the activity of those loose neutrons, had proved difficult.

It was up to Hungarian Jewish émigré Leo Szilard, who fled Hitler in 1933, to establish, while at Columbia University, that fission of uranium produced more neutrons than it consumed, and it was up to Enrico Fermi, another émigré fleeing persecution in Italy—his wife was Jewish—to construct the first nuclear reactor, known as Chicago Pile-1, or CP-1.  (Fermi is the “Italian navigator” mentioned in the coded message above, and CP-1 is the “pile” referred to in the above quote)

CP-1

Pile was a very appropriate descriptor, as, in the words of Fermi, his primitive reactor was “a crude pile of black bricks and wooden timbers.”  The final structure required 45 tons of uranium oxide and 5.4 tons of uranium metal, all encased in 45,000 ultra-pure graphite blocks weighing a total of 360 tons.  (Graphite was the moderator needed to control the activity of the neutrons; heavy water, the only other suitable moderator, was too difficult to obtain in large quantities).  When completed, the elliptically-shaped pile stood 20 feet high, 6 feet wide at the ends, and 25 feet across the middle.

The team that worked on CP-1. Fermi is front row, on left; Szilard is second row on right (in white trench coat)

On the fateful afternoon of December 2, 1942, CP-1 was ready.  The control rods were slowly removed, and pile went critical (self-sustaining) at 3:25 PM.  Having run for approximately 4-5 minutes, and having generated about 0.5 watts of power, it was shut down.  A scientist in the party opened a bottle of Chanti, and all toasted the event from paper cups.  It was the first demonstration that a nuclear device was now feasible, a turning point in the evolution of the Manhattan Project, with consequences we are still living with today.  As Leo Szilard observed when he at last proved fission was possible: “That night, there was very little doubt in my mind that the world was headed for grief.”

At The Lanier Library

This past Thursday I gave a lecture at The Lanier Library (where I am a proud member of the board), located in my hometown of Tryon, NC. The talk was entitled “The Heavy Water War: Stopping Hitler’s Atomic Bomb.”  It focused on the years-long struggle by the Allies to prevent the Germans from obtaining heavy water—a crucial moderator, as noted above—from the only available source, a facility in Rjukan, Norway.  After my talk ended, a library member named Betty, sitting in the front row, approached me, and shared with me that her mother had worked on CP-1 during the war years, and for her efforts, had been awarded a piece of the graphite pile used.  Here it is:

Graphite from CP-1

Talk about a small world!  Thanks again, Betty!

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