Sunday, November 26, 2017

The Day the Atomic Age Was Born

Anniversaries are always important. Most are personal, but a few are for everyone. For example, December 2017 is the 75th anniversary of "Casablanca," the iconic film that captured the zeitgeist of the 1940s.

It is also the 75th anniversary of something else -- an event so momentous it's no exaggeration to say it changed the world. It happened on the campus of the University of Chicago, my school, where I did graduate work in chemistry many years ago. (My wife and I were newlyweds at the time, she an English major.) On my way to the chemistry labs each day, I walked past the Henry Moore sculpture that commemorates the event. Tour buses drove past it as well.

I'm talking, of course, about the first controlled self-sustaining nuclear reaction -- the lynchpin of the Manhattan project, the seminal event that ushered in the atomic age. And, as all schoolchildren know, the endgame was Hiroshima and Nagasaki and the horrendous destruction that ended World War II.

Much has been written about Chicago Pile-I. A great read is Segre and Hoerlin's "The Pope of Physics," a breezy biography of Enrico Fermi that chronicles the splitting of the atom.

The atomic age was born on December 2, 1942, on a squash court under the west stands of Stagg Field. The centerpiece of the experiment was a 400-ton layering of solid graphite bricks and bricks embedded with uranium and uranium oxide. As described in the University of Chicago Magazine, fast neutrons released by the decaying uranium were slowed by the graphite so they could be captured by other uranium nuclei, inducing more fission. Cadmium rods inserted into the pile absorbed the slowed neutrons, in turn controlling the chain reaction.

That this happened on the Chicago campus at all was a fluke. For safety reasons, it was scheduled at a remote site in the Argonne forest southwest of the city (now the Argonne National Laboratory). But a worker's strike shut down construction of the building that was to house the pile. Fermi and his colleagues decided not to wait for the strike to end, but instead to build the pile themselves and to do it in a setting so mundane that few would notice.

The story is amazing, filled with vignettes and homely touches -- very much a story of its time.

  • Robert Hutchins, the iconic president of the University of Chicago, was never told of the risky experiment about to take place in an area amidst thousands of students. The scientists were afraid Hutchins would deny permission.
  • In a show of teamwork that would be impossible today, players from academia, the military and the private sector built the pile in 15 days!
  • The orchestrator of it all, Enrico Fermi, a native of fascist Italy, almost didn't make it to December 2. His classification as an enemy alien was lifted just two months earlier.
  • On the fateful day, as the cadmium rods were removed and the radiation mounted, Fermi halted the experiment. "I'm hungry," he said. "Let's go to lunch."
Later the experiment was resumed and the pile went critical. Forty people were there, crowded into the hidden squash court. Forty people witnessed history. As the last cadmium rod was withdrawn, Fermi said, "The reaction is self-sustaining. The curve is exponential." Atomic power had been unleashed. It was 3:53 p.m. and the world would never be the same.

The cadmium rods were reinserted and the chain reaction shut down. It had indeed been a controlled experiment. Only half a watt of power had been generated.

Arthur Compton, a Nobel physicist and major player in the Manhattan Project, called his counterpart, James Conant in Washington DC. His words would become famous: "The Italian navigator has just landed in the new world."

CP-I was only the beginning, of course. Uranium was enriched in quantity in Oak Ridge, Tennessee. Parallel work with plutonium was conducted in Hanford, Washington. And, as everyone knows, the bomb itself was developed in Los Alamos and tested 160 miles south in the New Mexican desert. The scientists and engineers who ran the Manhattan Project would become household names. Along with Fermi, Compton and Conant, there was Oppenheimer, Lawrence, Weil, Greenewalt, Teller and many others.

That was a long time ago. The university has changed. The west stands of Stagg Field are long gone, replaced by Mansueto Library. Also gone is Kent Laboratory, where Harold Urey had separated heavy water in a stairwell distillation column just a few steps from my laboratory in an adjoining building. Gone too is the rooftop promenade where I carried out sunlight-driven photochemical reactions long before solar power became fashionable.

But recollections remain. I remember Carolyn Scott, an undergraduate classmate, tell of a party her parents, surgeons at Chicago's Billings Hospital, hosted on the day the Japanese surrendered. Professors at the party, freed of their secrecy oaths, one by one told their wives they had helped build the atomic bomb. Scottie never forgot that. It made an impression on a young girl.

And what started on that remarkable day 75 years ago continues to impact the world. It spawned nuclear power plants that generate 20% of our electricity. It ended one war and averted others. It supported some governments and toppled others. It led to weapon proliferation that dominates our news today and shapes world policy.

Love it or hate it, Chicago Pile-I changed everything. The genie can never be put back in the bottle.

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