Oak Ridge, TN: Uranium Enrichment

(Satellite)

Rich Showalter posted
Women at work inside the K-25 uranium enrichment facility in Oak Ridge, TN.

Ni Zu: ....and now we have automation...

Rob Walker: Interesting story about these women. They were non technical high school graduates. It was believed that they would “tinker” with the Calutrons less than the scientists. They would simply run the equipment as they were taught. Many had no idea what they were actually working on.

https://time.com/5191480/atomic-city-womens-history/

Mike Andrews: Rob, exactly. And the the control panels were designed to as to reveal as little information as possible about just what they were controlling.

Sandy Hawkins posted

Y12 plant Oak Ridge TN 1944. These are the controls for gaseous diffusion of enriched uranium.

Michael White commented on Rich's post

These young women were operating the Calutron mass spectrometer enrichment machines at the Y-12 facility at Oak Ridge. They could focus the matter beams much, much better than the scientists who built the machines. And indeed, they didn't know what they were actually working on.

"We can train you how to do what is needed, but cannot tell you what you are doing. I can only tell you that if our enemies beat us to it, God have mercy on us!"

Navin Johnson posted

Almost ten thousand girls right out of high school were hired in Oakridge Tennessee in 1943, to operate mass spectrometers called Calutrons. They weren't even told what they were doing. They were only told to turn this knob, flip this switch, make this meter read a certain level. But they were enriching Uranium and it took them two years to make enough material for one bomb, the one dropped on Hiroshima. 

My mother-in-law was one of these "Calutron Girls". Whenever I asked what she did at Oakridge she would say, "if I told you, I would have to kill you! It was something for the war effort". I assumed she was a secretary. 

Then in the 90's, after things were declassified, I printed this picture from the internet and showed it to her, asking if this is what she did. She said, "Yeah! That's where I worked!! In building Y-12!  I'm not sure she ever knew what those machines did.

History's Mirror posted

The S-50 Thermal Diffusion Plant in Oak Ridge, Tennessee, was a critical but short-lived component of the Manhattan Project. As the third major uranium enrichment facility built during World War II, S-50 complemented the Y-12 Electromagnetic Plant and K-25 Gaseous Diffusion Plant, each representing different approaches to the same urgent goal: producing enough enriched uranium for an atomic bomb. Unlike its counterparts, S-50 used thermal diffusion to slightly enrich uranium before it passed through K-25 and then Y-12 for further refinement. Approved by General Leslie Groves on June 24, 1944, S-50 was rushed into service—operational by September 16 of that year, just 69 days after construction began. This haste came at a cost, with the facility suffering a high accident rate, though fortunately no fatalities occurred.

Despite its operational success, S-50 was rendered obsolete by the more efficient K-25 plant and was shut down on September 9, 1945, shortly after the end of the war. Its columns were removed, and the facility was repurposed for the Nuclear Energy for the Propulsion of Aircraft Project until 1951. S-50 was ultimately dismantled, but its contribution marked a unique and intense chapter in the story of atomic development.

Brad Woods posted 13 photos with the comment:

Y-12  ELECTROMAGNETIC SEPARATION FACILITY,  Oak Ridge, Tennessee.  In an effort to produce enriched Uranium-235, Oak Ridge utilized three separate methods, electromagnetic separation, gaseous diffusion and thermal (steam) separation. 

The Electromagnetic separation method, using a modified cyclotron, called a "Calutron" was the first method to be used at Oak Ridge. The first stage units were known as Alpha Units, later Beta Units were used to take the partially enriched feed from the Alpha Units and enrich it to weapons grade.

Oak Ridge was the first  geographical site, of the Manhattan Project, to be selected by General Groves,  in the massive drive to develop an atomic weapon.  He selected Oak Ridge from a sparsely populated ridge area in September 1942.  In less than a year, the first Alpha unit became operation.

The units worked, but created very small amounts of enriched U-235 per unit.  Grove continually added on units. Because copper was scarce during the war, silver was borrowed from the Treasury department which was formed into coils of the giant electromagnets in the Calutrons.  Two years later, over 22,000 people were being employed just in the Y-12 complex.  Most of these were young women, many of who had just graduated from college.  Colloquially known as "Calutron Girls."  They were not told what the machines controlled, how they functioned, nor what was being made.  They were simply trained to monitor gauges and alter controls in response to changes.  In Oak Ridge, knowledge was compartmentalized.  You were told what you needed to do your job and nothing else.  Codes or codewords were used for Uranium, many chemicals and many processes.  You were not allowed to discuss your job with anyone.

Eli Benson: The “Calutron Girls” were following a written protocol to adjust the machines based on gauge readings. A rivalry developed between the engineers and the Calutron Girls about who was doing the job the best. The engineers with their innate knowledge of the process, or the girls that read the gauges and adjusted the machines accordingly. The girls won the competition.

Stephen Bitmead: If I remember from reading a very exhaustive book on this, I think these devices were used eventually to further enrich the uranium from the gas diffusion units. That way the process became quite efficient. As this post says they weren’t good at enriching the raw uranium, but once it had been enriched to a certain level, they were quite good at getting them to the final required level of enrichment.

Brad Woods: Stephen Bitmead Yes, that is why the he electromagnetic process had to have two stages. K-25 was not fully functional until after the war, so they used the first few stages of it, which were functional, and used that as feed material for the Calutrons. As you indicated, this increased production efficiency greatly.

Brad Woods: Eli Benson Exactly. They put the engineers in their place. After working their machines for 8 hours shifts for months they got used to the machines individual peculiarities and could run them with fine tuned precision.

Rod Stadum: Jun Santos I've read that the Project requested virtually all of the silver the Treasury had, for conductors. Copper was needed on the frontlines for shells.

Peter Beringer: Ohh, I don’t know anything about “thermal (steam) separation”! A little surprised, given my tendency to become obsessed with obscure aspects of the history of nuclear technology. Guess I got a date with the Google machine!

Brad Woods: Peter Beringer Look up the "S-50" facility at Oak Ridge. It was located near K-25 along the Clinch River . We don't hear as much about it as it was the last separation plant to go online in Oak Ridge. It was not operated for a long time.

https://www.osti.gov/opennet/manhattan-project-history/Places/OakRidge/oak-ridge-s50.html

Albert LaFrance: I wonder what variables the operators monitored and controlled. I'd love to see the user manual for that equipment! To assess production, maybe they watched the beam currents through the two collection pots?

Brad Woods: Albert LaFrance I don't know all the variables, but they did monitor the voltage to the filaments in the heaters that vaporized the Uranium compound, the strength of the magnetic fields, and as you say, the current for the ion beams. I would imagine they had to monitor the vacuum pressure in the "D" chambers for leakage as well. The developer of the Calutrons was the physicist Ernest Lawrence. He often visited Oak Ridge to see/oversee the installation and running of his machines. He took great pride in them. The Calutrons girls were often not so happy to see him. Of course, they didn't know the functions of the machines nor what their actions inputed on the controls did, but they were quite adept at keeping the Calutrons operating within their designed parameters. Lawrence would walk around up and down the isles and occasionally go to a console and tweak with it in an attempt to improve performance. He would get frustrated glares from the girls as oftentimes he failed and messed the girls console controls up so badly that had to go back and recalibrate it from start. In one case Lawrence actually shorted out one of the girl's machine trying to push it to its limits. As someone mentioned earlier, the girls knew the idiosyncrasies of their particular machine and could operate it with fine controlled precision. All too often, a smug scientist or supervisor, thinking they could show the girl how to do it better, got humiliated as they crashed the machine. Adding insult to injury were the barely suppressed giggles of the other operators!

John Post: I’m thinking Los Alamos was the first site….?

Brad Woods: John Post Oak Ridge was the first of the three sites selected by General Groves.

The time line was very close, John. Oak Ridge was selected in September and Los Alamos not until November. By February Oak Ridge had already started construction of the Y-12 plant. Los Alamos was not deemed a lab until April. So yes, the time differences are subtle as all three sites were progressing concurrently. Los Alamos was dependent on Oak Ridge for fissionable material for their experimental work. Although they had many meetings at Los Alamos, and we're doing mathematical modeling, they could not do their physical bomb construction experimental work until they started receiving Plutonium for Oak Ridge's X-10 reactor and Enriched Uranium from Oak Ridge's Y-12 plant.

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A rare look into the inside of a Calutron Control unit. The picture is not clear, but at the top of the units, you can see the name of the manufacturer, General (GE) Electric.

Albert LaFrance: Do you know where these panels were located in relation to the actual calutrons? It looks like the there's some high power/voltage equipment and plumbing (vacuum system?) inside, so I'd assume they were in close proximity.

Brad Woods: Albert LaFrance Good question. They were adjacent, but the panel operators were not permitted into the calutron areas. The panels or cubicles not only allowed control but provided power to each "D" unit to heat the Uranium compound and vaporize it. The D units were operated at a vacuum.

Mark Saxton: https://www.y12.doe.gov/.../assets/document/08-01-03.pdf

Mark Saxton commented on photo 5.

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End of shift! The "CEW" on the sign stands for Clinton Engineering Works, which was the official name of the Oak Ridge Facility used by the Government.

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One of the "D" units, which was a tank that would be housed between electromagnetic coils and contained the Uranium. The vaporized U-25 and U-238 followed different arcs due to their difference in molecular weight. Two small bins collected the enriched Uranium and the depleted Uranium at the end of the arcs.

Dan Reinhart: So, it condensed within the equipment?

Brad Woods: Dan Reinhart Yes, the ion streams ended in a "collector box." Technicians periodically took these out of the machines and removed the enriched material (plus all of the other gunk that inadvertently condensed out all over the inside of the machine.)

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Exterior of one of the Alpha buildings.

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Many "D's" put together formed a "racetrack." Each D had a control panel. Often an operator had responsibility for two panels or "consoles." (usually a young woman, known as a "Calutron Girl.') Racetrack technicians have many stories. Walking on top of the racetracks, is stated as like trying to walk through a vat of honey. The great magnetism from the electromagnets below their feet pulled on the nails in their shoes making walking a concerted effort. Women reported bobby-pins being pulled from their hair. One worker was carrying a sheet of steel, when he got too close to the calutrons the magnetism yanked him over to the machine and trapped him between the steel sheet and the side of the unit. Power had to be turned off to extricate him (he was not seriously harmed.)

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Construction of alpha and Beta electromagnetic separation buildings never seemed to cease.

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Joe Osullivan: I would imagine these photos would have been highly classified at the time.

Brad Woods: Joe Osullivan Absolutely!