5 ms·

That rendition confuses me a lot. What are they doing? Besides being obviously stupid, how is anything useful coming out of that? It doesn't look like anybody

That rendition confuses me a lot. What are they doing? Besides being obviously stupid, how is anything useful coming out of that? It doesn't look like anybody is actually measuring anything useful. He's randomly wiggling that screwdriver back and forth, but what for? Is somebody collecting data for a table or a graph? Shouldn't the separation distance, or angle, or something being carefully measured and controlled?

russdill 3y ago
During the incident, he was demonstrating the technique necessary to Graves, not performing an actual experiment. He was a bit of a show-off and was doing the demonstration without shims that would have prevented criticality. And yes, all they had were the counters. Other than that, the video is really inaccurate.
petsfed 3y ago
One of the things I noticed with the experiments I participated in was that while the drama was very real for me, to an outside observer, its actually kind of dull. To keep the pacing tight and keep the audience interested, they have to spice it up a bit. As I understand it, Slotin was demonstrating to another colleague how to test the distance dependence of criticality, so the data collected was less valuable to the demonstration than the procedure. I think the creative license here was the second screw driver to make it look more sciencey. Holding one half of the beryllium sphere with a bare hand (as was part of the approved procedure) probably felt a little too slap-dash, and the fact that Slotin's procedure involving a screw-driver was unapproved in the first place undermines the role of the scene to call out the government's lack of care for Cusack's American-everyman character. If there's a (tenuous) moral to be extracted from the incident, its that Slotin apparently believed in the cowboy persona he projected, and it cost him his life.
- petsfed 3y ago
  I want to be very clear here that I don't actually think there's much moral to this story. They had an idea of how bad criticality could be, but there was no real deterrent other than Fermi telling Slotin and others that if they kept up the procedure, they'd be "dead within a year". That tells me that everybody, from Oppenheimer on down, did not understand just how dangerous this sort of demonstration could be. Given the era, that's pretty understandable.
ortusdux 3y ago
The more you contain the plutonium core within something that reflects neutrons, the closer it gets to going critical. In this case, they used two half spheres of beryllium as reflectors. The screwdriver was used to adjust the amount of neutrons reflected, and the results were measurable on a Geiger counter. I believe the goal of this technique was to compare their calculations to the real thing.
- dale_glass 3y ago
  Right, but there's no actual measurement being done, nor it could be done, unless there was some guy there measuring the separation with calipers or something. So what's the point, simply to practically demonstrate that less distance = more radiation? I guess that makes some sense, but it seems too trivial of a thing to demonstrate to people in a high level, secret operation. I'm just imagining that for this to actually produce some sort of useful result there needs to be some sort of precise measuring happening. Maybe moving half the sphere with a screw and having a dial indicator there, or something.
  - ortusdux 3y ago
    As I understand it, this was just a demonstration of the technique. The actual experiment called for metal shims between the cores, which I assume were of known thicknesses. Also, from the American Physical Society's writeup: "Nine days after the accident, Slotin died after “a total disintegration of bodily functions.” Ironically, he had become disillusioned with the postwar atomic tests, and one reason for that ill-fated experiment was to train a replacement, so Slotin could resume his prewar research in biophysics and radiobiology at the University of Chicago. He never got that chance. In response to his death, Los Alamos ceased all hands-on experiments with critical assemblies, using remote controlled machines to protect the operators. As for the killer “demon core,” it was used in one of the first postwar atomic bomb tests at Bikini Atoll, a mere five weeks after Slotin’s death. The test went off without a hitch." https://www.aps.org/publications/apsnews/201405/physicshistory.cfm https://www.aps.org/publications/apsnews/201405/physicshisto...
    - 3y ago

russdill 3y ago

During the incident, he was demonstrating the technique necessary to Graves, not performing an actual experiment. He was a bit of a show-off and was doing the demonstration without shims that would have prevented criticality. And yes, all they had were the counters. Other than that, the video is really inaccurate.

petsfed 3y ago

One of the things I noticed with the experiments I participated in was that while the drama was very real for me, to an outside observer, its actually kind of dull. To keep the pacing tight and keep the audience interested, they have to spice it up a bit. As I understand it, Slotin was demonstrating to another colleague how to test the distance dependence of criticality, so the data collected was less valuable to the demonstration than the procedure. I think the creative license here was the second screw driver to make it look more sciencey. Holding one half of the beryllium sphere with a bare hand (as was part of the approved procedure) probably felt a little too slap-dash, and the fact that Slotin's procedure involving a screw-driver was unapproved in the first place undermines the role of the scene to call out the government's lack of care for Cusack's American-everyman character. If there's a (tenuous) moral to be extracted from the incident, its that Slotin apparently believed in the cowboy persona he projected, and it cost him his life.

petsfed 3y ago
I want to be very clear here that I don't actually think there's much moral to this story. They had an idea of how bad criticality could be, but there was no real deterrent other than Fermi telling Slotin and others that if they kept up the procedure, they'd be "dead within a year". That tells me that everybody, from Oppenheimer on down, did not understand just how dangerous this sort of demonstration could be. Given the era, that's pretty understandable.

ortusdux 3y ago

The more you contain the plutonium core within something that reflects neutrons, the closer it gets to going critical. In this case, they used two half spheres of beryllium as reflectors. The screwdriver was used to adjust the amount of neutrons reflected, and the results were measurable on a Geiger counter. I believe the goal of this technique was to compare their calculations to the real thing.

dale_glass 3y ago
Right, but there's no actual measurement being done, nor it could be done, unless there was some guy there measuring the separation with calipers or something. So what's the point, simply to practically demonstrate that less distance = more radiation? I guess that makes some sense, but it seems too trivial of a thing to demonstrate to people in a high level, secret operation. I'm just imagining that for this to actually produce some sort of useful result there needs to be some sort of precise measuring happening. Maybe moving half the sphere with a screw and having a dial indicator there, or something.
- ortusdux 3y ago
  As I understand it, this was just a demonstration of the technique. The actual experiment called for metal shims between the cores, which I assume were of known thicknesses. Also, from the American Physical Society's writeup: "Nine days after the accident, Slotin died after “a total disintegration of bodily functions.” Ironically, he had become disillusioned with the postwar atomic tests, and one reason for that ill-fated experiment was to train a replacement, so Slotin could resume his prewar research in biophysics and radiobiology at the University of Chicago. He never got that chance. In response to his death, Los Alamos ceased all hands-on experiments with critical assemblies, using remote controlled machines to protect the operators. As for the killer “demon core,” it was used in one of the first postwar atomic bomb tests at Bikini Atoll, a mere five weeks after Slotin’s death. The test went off without a hitch." https://www.aps.org/publications/apsnews/201405/physicshistory.cfm https://www.aps.org/publications/apsnews/201405/physicshisto...
  - 3y ago