[mclau157]

Before there was any bomb there was the Chicago Pile-1 in the middle of Chicago in a space under the stands at Stagg Field originally built as a rackets court

A wooden frame supported an elliptical-shaped structure, 20 feet high, 6 feet wide at the ends and 25 feet across the middle. It contained 6 short tons of uranium metal, 50 short tons of uranium oxide and 400 short tons of graphite, at an estimated cost of $2.7 million. According to Robert Crease, CP-1 and preceding piles were "the largest unbonded masonry structures since the pyramids.

On December 2, 1942, Fermi announced that the pile had gone critical at 15:25. Fermi switched the scale on the recorder to accommodate the rapidly increasing electric current from the boron trifluoride detector. He wanted to test the control circuits, but after 28 minutes, the alarm bells went off to notify everyone that the neutron flux had passed the preset safety level, and he ordered Zinn to release the zip. The reaction rapidly halted. The pile had run for about 4.5 minutes at about 0.5 watts. Wigner opened a bottle of Chianti, which they drank from paper cups.

[sherr]

The Rhodes book is great on this. Fermi was such a good physicist and a great hands-on engineer. Before electronic calculators or computers: a slide-rule, graphing paper and a notebook. A lot of danger getting the maths wrong! Luckily, Fermi was very good at maths.

[ggm]

The article quotes extensively from Rhodes, and Groves.

[toxic72]

I have in my possession a chunk of one of those graphite bricks. Very neat piece of history.

[germinalphrase]

How did you come by it?

[rbanffy]

> but after 28 minutes, the alarm bells went off to notify everyone that the neutron flux had passed the preset safety level

Really feels like catching the dragon by its tail.

[HPsquared]

Imagine the fallout (literally and figuratively) if they'd gotten the calculations wrong.

[HPsquared]

Was there ever a radiation hazard from that or a big cleanup? Seems very "early days safety standards".

[pfdietz]

That reactor was run at a very low power level, so there was little activity. It was dismantled in 1943 and the parts moved to make CP-2 near Chicago at a site that later became Argonne National Laboratory. CP-2 had shielding (but no cooling) and operated at a few kilowatts.

[euroderf]

> Before there was any bomb there was the Chicago Pile-1 in the middle of Chicago in a space under the stands at Stagg Field originally built as a rackets court

Groves's book ("Now It Can Be Told") mentions the people that worked with the graphite bricks, that it got into their skin, and even after an after-work shower, they'd still ooze graphite for hours.

Firstly I wonder what their cover story for their spouses was.

Secondly it's clear that they should've had an on-site sauna. Get some deep cleaning going. That would've flushed the graphite gunk out of their hides.

[cyberax]

When the USSR was building the bomb, the director of the graphite manufacturing company unofficially asked Kurchatov (the lead scientist of the Soviet nuclear project) to bring him a handful of diamonds.

He assumed that graphite of such high purity can be useful only for this purpose during the wartime.