This is why I’m not a nuclear physicist

It’s just too scary, and radioactive materials are just too weird.

The metal rods in the top photo are plutonium. Rods can roll. These rods could roll closer to each other and perhaps produce the kind of runaway neutron reaction that killed Slotin and Daghlian. Putting a hand in to separate them could make the reaction worse because the water in a human body reflects the neutrons.
I had formal safety training, informal discussions with more experienced people, and made it a point to internalize rules of thumb. Keep pieces of plutonium separate. Abide by glovebox limitations; every glovebox has a sign with the limits of plutonium allowed in it. For solutions, keep them dilute and in flat containers. Flat/thin is safer; the closer a shape is to spherical, the less material is needed to go critical. IIRC, there were racks to put rods in if you were working with that shape of metal, so that they didn’t accidentally roll together.

Daghlian and Slotin? I made the mistake of looking them up and finding out about the Demon Core.

My version of safety rules is don’t eat sandwiches in the lab, don’t drink the mystery fluid in that test tube, wear latex gloves when playing with the nasties, the lab alcohol is not for parties, and wash your hands every once in a while. “Don’t let these two tubes touch each other, or invisible rays will instantly flash out and kill everyone in the room in slow grisly painful ways” isn’t part of the set of instructions I have to give students.


  1. jrkrideau says

    Reminds me of my Grade 12 and 13 chemistry teacher who routinely used a lab beaker as a water glass. I expected him to keel over almost every class.

    Last I heard he died at roughly 88 years of age. Still scares the hell out of me.

  2. blf says

    Why the feck are the rods made in a shape which can (easily) roll?

    A non-rolling shape — say, triangular — wouldn’t prevent variants, such as being (accidentally) placed / knocked too close together. But, perhaps naïvely, it would seem to significantly reduce a set of risks at an acceptable cost.

  3. Mobius says

    I remember Daghlian from Fatman and Little Boy. Sad story. Didn’t know about Slotin.

  4. The Very Reverend Battleaxe of Knowledge says

    For many years, I always read that the Demon Core was expended in Crossroads Able, but the story now seems to be that it was melted down. Who knows what really happened?

  5. Doc Bill says

    I had colleagues who used beakers for coffee and tea. I could never bring myself to do that. Some years ago a friend bought me a set of beakers with handles, designed to be used as coffee/tea cups and I quietly discarded the gift.

  6. Igneous Rick says

    Physicists, biologists, and chemists have all these rules. I think the most strident warning I ever received was “don’t lick the rocks that smell like sulfur.”

  7. themadtapper says

    Slotin, who was given to bravado, became the local expert, performing the test on almost a dozen occasions, often in his trademark blue jeans and cowboy boots, in front of a roomful of observers.

    What is it about cowboy outfits that bring out the stupid in people? Or is it stupidity that brings out the cowboy in people? Bringing in an audience and using improper tools to show off how awesome he was. It’s a wonder he only managed to kill himself with his stupidity and not everyone else in the room, or in the whole facility for that matter.

  8. Alt-X says

    Reminds me of a time I got a job offer at an exploration mining company. They winch radioactive material down a deep hole and run tests. At the meeting the manager shows me a big metal container, holding the radioactive material, in the middle of their parking bay, on the ground floor of the office. He points it out, I walk up to the container, just sitting there, not knowing what I’m suppose to say or do. I stop about a meter away and I’m stand there looking at it, nodding approvingly (fake it till you making it, right?) he looks over to me and says “yeah it should be safe for you to be that close”. Should be! Should be?! Bloody hell, I took a giant step back. As soon as the meeting was over, I noooped the hell out of there and politely said #$%@ no to the offer via email! What the hell kind of a joke of a company leaves radioactive material sitting in a parking lot, INSIDE their office?! Should Be safe!? God damn! If my legs fall off when I hit 60, I’ll know who to blame!

  9. davidc1 says

    I thought all nuclear stuff was bright green ,like wot it is in the Simpsons .

  10. microraptor says

    Alt-X @9:

    Back in my freshman year of college, first day of chem lab we got to hear the story of how someone was rummaging around in one of the lab’s storage closets when they discovered a dusty, unlabeled box. It turned out to contain a dangerously radioactive isotope that had just been sitting in the back of that closet for who knows how long because nobody had thought to question what was in the box.

    I don’t actually know if that was a true story or not, but the moral was that we were absolutely not to assume that anything we found in the lab was safe if we didn’t know what it was.

  11. says

    It’s a wonder he only managed to kill himself with his stupidity and not everyone else in the room

    Several of the other people in the room were severely irradiated but lived.

    I wonder if anyone has ever done a comparison of cancer rates among manhattan project workers compared to the rest of the population.

  12. komarov says

    Hands-on criticality experiments were stopped, and remote-control machines and TV cameras were designed by Schreiber, one of the survivors, to perform such experiments with all personnel at a quarter-mile distance.

    It only took two major accidents and deaths for them to decide to separate the experimenter and the deadly material? Are nuclear physicists are the reckless blockheads of the physical sciences?
    “Let’s smash these volatile bits here together and see what happens.” – “What if nothing happens?” – “Why, we’ll use bigger bits and smash them together much harder until something does happen, of course!” – “Of course!”

    I think now I know where the Dangerous Experiment By Arrogant Scientists Goes Horribly Wrong-Trope comes from.

  13. Callinectes says

    My only rule in the lab was “separate fridges for lunches and specimens, not separate shelves.”

  14. says

    Nuclear physicist are a scary bunch.
    Reading up on early reactor tests gives me goosebumps. While it is most likely a myth that “SCRAM” stand for safety control rod ax man, that it is believable shows a lot about this time.
    People with a minimum of understanding of fission physics (it was a new field, naturally understanding was limited) designed reactors and tested them in universities and other well populated areas. That nobody got hurt or died at that time shows a good deal of luck and some very good theoretical models.

  15. chrislawson says

    Another horrifying example: the Goiânia accident. Four deaths (including a 6-year-old child), 249 people contaminated, and the primary cause of the accident was a slow trainwreck confluence of administrative, legal, and financial myopia despite clear and repeated warnings from the owners of the machine (who were prevented by court order from decommissioning it).

    I find this even more terrifying than the Demon Core story because it shows you don’t need to work in nuclear physics to be endangered, you don’t need the scientists to be cowboys, and you don’t even need to live close to the original location.

  16. says

    SL-1 is another good example of how scary early nuclear physics/power was. I had been trained on a modern reactor before I learned about it so every detail of the design and operation was horrifying.

    A dude standing on the top of the reactor vessel pulling a control rod, one of just 3, by hand? Fuck that shit.

  17. mareap says

    I was at grad school with Palmer Graves, son of Alvin Graves who was present at the second accident (and mentioned in the Wikipedia article). Boy, did he have stories to tell!

  18. nelliebly says

    WTF?! Was…was risk management just not a thing then?

    I’m currently working on a project to provide a safety backup system to a large industrial system, and everything is about taking human intervention to an absolute minimum. All the hazards have to be identified, managed and independently audited before we’re allowed to hand the system off to the customer.

    Safety critical systems are srs business.

  19. embraceyourinnercrone says

    Somewhat related:

    Apparently being too lax with safety concerns crosses fields (at least if the hair raising stories in the comments are true)

    “A notice had come out to everyone about old peroxide-forming reagents needing to be disposed of, especially in the non-chemistry labs. The biology lab head involved read this, noted the part about possible crystalline peroxide formation, went over to a cabinet and rummaged around for an elderly can of diethyl ether in the far back corner, and then shook it next to their ear to see if it sounded like had deposited any solid.”

  20. a_ray_in_dilbert_space says

    I am a nuclear physicist of sorts–actually, a physicist specializing in the effects of radiation in semiconductors. I’ll just point out that radiation was still a fairly new phenomenon at the time. X-rays were discovered only 50 years before the first nuclear test. Up to the 1930s people used to go to radium spas to inhale the “healing vapors”. Also, if you are going to think about it “rationally” like a physicist, the energy imparted by a radiative decay is tiny–if it were heat energy, you wouldn’t even feel it. And we’re surrounded by radiation–we get a dose from radioactive potassium every time we eat a banana. What was missing from their understanding was biology–the essence of heredity and genetics in DNA.

    We still do not fully understand the mechanisms by which radiation damages DNA. NASA has a lab dedicated to the study of genetic and tissue damage by highly energetic, highly charged ions like galactic cosmic rays (look up HZE radiation).

    And now that the mechanisms are somewhat understood, most radiation physicists are pretty safety conscious. I get more dose on the plane ride to the cyclotron than I do at the cyclotron–although, it does seem to make the flight attendants nervous when I pull out my geiger counter to measure the neutron flux at altitude, especially near the poles.

  21. yaque says

    Wanna really freak out?
    an air-cooled nuclear reactor

  22. says

    A neighboring university has a low yield nuclear reactor for neutron experimentation. This thing is build so save they let students run it.
    They can also pulse it, basically shooting out one control rod and let the reactor go prompt critically, as in start to explode. Oh and the reactor cover is see through.
    Which meant that while i was visiting that university, i could stand on top of the reactor while they shot out the control rod and see how every thing started to glow blue, thanks to the Cherenkov Radiation.
    Fun times :D

  23. komarov says

    Re: a_ray_in_dilbert_space (#22):

    From the Demon Core wiki article:

    Enrico Fermi reportedly told Slotin and others they would be “dead within a year” if they continued performing [the experiment]. Scientists referred to this flirting with the possibility of a nuclear chain reaction as “tickling the dragon’s tail”, based on a remark by physicist Richard Feynman, who compared the experiments to “tickling the tail of a sleeping dragon”.

    Clearly the scientists knew enough to realise how reckless they were being. And you don’t need to understand the mechanism to know something can easily kill you when you’re not careful.

  24. says


    Prompt Critical? That reactor must have had some serious measures to quickly add negative reactivity. Most designs I know of Prompt Critical means the core has melted before you even know you fucked up.

  25. says

    Certainly by major negative feedback, not saying that you’re wrong. From my training I eyeroll “the reactor is critical!” but prompt critical is pants shitting time.

  26. a_ray_in_dilbert_space says

    Oh, they knew it was dangerous–just now why it was dangerous, how dangerous it was or precisely wherein lay the danger. Marie Curie had died of radiation-induced cancer by this point, and the radium girls (who used radium paint to make watch dials glow) had actually sued their employers in 1938.

    All I’m saying is that there is a difference between a threat where you understand how it kills you and one where you don’t. The latter is more likely to cause both irrational fear and “hold my beer and watch this” bravado.

  27. drken says

    I always hated working with radioisotopes in the lab. I-125 was dangerous enough for me, I can’t imagine what working with plutonium must be like.

  28. cedrus says

    That said, there are biology labs that live a little dangerously. I’ve worked at BSL3; there’s a lot of this kind of “mechanical things that keep you from absent-mindedly killing yourself” involved. (Didn’t quite realize how much until I had to take a repairman in there, and yes the room had been decontaminated, but he was damn near licking the place clean…and it was physically painful to watch.)

  29. emergence says

    Wait, just banging plutonium rods together can generate a neutron blast? Why did the Los Alamos guys handle this stuff without protection for so long?

    About that SL-1 incident, I heard the guy on top of the reactor vessel got skewered to the ceiling when a control rod shot out.