Demon Core: The Strange Death of Physicist Louis Slotin | Hacker News Reader

Demon Core: The Strange Death of Physicist Louis Slotin

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85 pointsjseliger34 comments

Sounds like 'normalisation of deviance': when something is dangerous but has previously been done without incident, so it becomes standard procedure. NASA has some guidelines on eliminating it from your practices and systems: https://sma.nasa.gov/docs/default-source/safety-messages/saf...

I'm not sure I would go that far. Some considered Slotin's methods dangerous: 'Enrico Fermi himself had warned Slotin that he would be “dead within a year” if he continued'.

Depiction of the accident in the film "Fat Man and Little Boy": https://youtube.com/watch?v=0ZFPio2PeQc&t=6m24s

Scary.

That's a fictional depiction, including elements from both the Demon Core incidents. For example, there were no metal blocks surrounding the assembly during the incident that resulted in Slotin's death - that's from the earlier incident that led to the death of Harry Daghlian.

There is a fact-based dramatization of the incident on the Dark Matters TV show. Look for Season 2, Episode 4:

https://www.youtube.com/watch?v=HPFhKUt245E (Edited video source)

Link with exact time: https://youtu.be/HPFhKUt245E?t=1625

It's a great scene (even though it's highly fictionalized), and it's a shame that the film itself is so mediocre. In particular, Oppenheimer and Leslie Groves were horribly miscast. Sam Waterston in the Oppenheimer (1980) miniseries was much more true to life.

Speaking of criticality accidents... apparently Feynman had to convince a army colonel that the team doing the 235U enrichment at Oak Ridge need to be informed about the physics of what they were working with. Had he been unsuccessful, a much larger criticality "excursion" would have happened.

In the setup/practice runs of the enrichment facility they were using big carboys to move uranium nitrate solution. Nobody told them that water (as a moderator) would significantly amplify the chain reaction! According to Feynman, "...the plant would never work, it would have blown up - I swear it would've."[1]

[1] https://www.youtube.com/watch?v=hTRVlUT665U#t=2106

And indeed, many of the criticality accidents listed on the Wikipedia page https://en.wikipedia.org/wiki/Criticality_accident happened while handling fissile material in solution.

There is a very interesting book on criticality accidents, which includes photographs and sketches on laboratory layout etc.: McLaughlin, T.P., Monahan, S.P., Pruvost, N.L., Frolov, V.V., Ryazanov, B.G. and Sviridov, V.I., 2000. A review of criticality accidents 2000 revision (No. LA-13638). Los Alamos National Lab., NM (US). https://www.orau.org/ptp/Library/accidents/la-13638.pdf

Thanks for that great reference!

Another worthwhile read is "Nuclear Accidents" by James Mahaffey.

There's also a story (I barely remember so sorry for the detail) I thought you were going to say, the workers knew this stuff was dangerous in volume so they kept amounts in separate rooms. Unfortunately this was up against the same wall dividing the rooms. I don't think it was an accident it just underlines the importance of understanding.

I always found it interesting that only one person died in each "Demon Core" incident, despite the burst of radiation being so intense that it caused the blue flash. Mind you, many of the survivors suffered health problems that were likely caused by the incidents later in life: http://www.orau.org/ptp/pdf/accidentsurvivorslanl.pdf

Interestingly the blue flash was caused by electrons, which had been excited by the radiation, transitioning back to a lower energy state and giving off photons!

The reason people survived is because radiation from a source falls off by the inverse square law, so as long as you have a small source and a short burst of radiation, distance is great. It's more surprising to me that they didn't use more remote devices for these kinds of experiments.

>> It's more surprising to me that they didn't use more remote devices for these kinds of experiments.

They did, but these also caused accidents. See the Lady Godiva device: https://en.wikipedia.org/wiki/Godiva_device

Otto Frisch received a larger than intended dose of radiation when leaning over the original Lady Godiva device for a couple of seconds. He noticed that the red lamps (that normally would flicker intermittently when neutrons were being emitted) were 'glowing continuously'. Frisch's body had reflected some neutrons back to the device, causing it to go critical, and it was only by quickly leaning back and away from the device and removing a couple of the uranium blocks that Frisch escaped harm but, he said, "if I had hesitated for another two seconds before removing the material ... the dose would have been fatal". On 3 February 1954 and 12 February 1957, accidental criticality excursions occurred causing damage to the device, but fortunately only insignificant exposures to personnel. This original Godiva device was irreparable after the second accident and was replaced by the Godiva II.

If I understand this correctly (the closest I got to being a nuclear phycisist is having met an astrophycisist once) this happened during the setup of an experiment. I think normally the experiments with this device were sort of automated (they dropped a rod between two masses, so gravity killed the reaction quickly).

[https://en.wikipedia.org/wiki/Criticality_accident#Recorded_...]

According to wikipedia, the other people in the room in the second accident were shielded by Slotin's body.

In the first accident the scientist, Harry Daghlian, was working alone and the second victim, a guard was a sitting a few meters away (so I guess he too was probably shielded by Daghlian's body).

[1] https://en.wikipedia.org/wiki/Demon_core#Second_incident

Follow-up analysis: "The blue flash" by Alex Wellerstein

http://blog.nuclearsecrecy.com/2016/05/23/the-blue-flash/

I'd seen from a lot of other sources that the demon core was used in Crossroads Able, which also caused hearings and investigations due to it being dropped a significant distance from its intended point. Anyone have any better proof one way or another to say for certain what the Demon Core's fate was?

Alex Wellerstein just made a blog post which elaborates on how he knew it was melted down. Apparently the source is personal communication with Glenn McDuff, a retired scientist at Los Alamos.

http://blog.nuclearsecrecy.com/2016/05/23/the-blue-flash/

Thanks. That definitely sheds more light, even though I will admit I have some partiality to the romantic notion that it was jinxed even in its last excursion into criticality.

Amazing that it working on that stuff was an individual experiment, with your hands in the mix!

People knew in general far less about the effects of ionizing radiation at the time --- you could even say Slotin's death was one of the datapoints that lead to better understanding.

I just finished watching the TV series Manhattan, about the Manhattan project. It was supposedly written with help from historians and physicists who know their stuff. This reminded me of one of their plot points that seemed realistic - a character suffered a potentially dangerous exposure, and the base doctor, feeling out of his depth, tries to reach out to somebody who knows better. After a few hours of chasing bureaucracy and secrecy, he eventually discovers that the official expert is listed as himself! There really isn't anybody who has any idea how exposure affected people, and they're just pushing ahead anyways because it's wartime.

To say that people were cavalier about the dangers of radiation back then would be a severe understatement.

They weren't that cavalier, else, for example, a lot more people working on the project, especially at the fissionable production plants, would have died from radiation exposure, instead, it was just these two working on the Demon Core.

This feels more like arrogant scientists believing the rules didn't apply to them, that particularly true for Daghlian, who was for example violating the very sensible rule that you don't work on this sort of thing alone (e.g. a coworker might have pointed out the danger of the experiment, or independently taken more effective action to stop it before fatal dosing happened, e.g. partly in the manner that Frisch saved himself, by knocking aside some of the reflecting blocks instead of Daghlian's attempt to remove the block he'd dropped).

(See also the Los Alamos team of junior scientists who violated both direct orders and all common sense in trying to whip up their own smoke pots, resulting in as I recall one death and one blinding. I knew better than that when I created my own pyrotechnics in high school (granted, I'd been on the track to become a scientist since 1st grade, but...).)

Seriously, Slotin should have either realized the danger if his hand slipped, or should have realized that his hand slipping was too great a risk for really no serious gain.

It was, even by the standards of the day, incredibly careless.

I've been thinking the same, but might it be that being in such a hurry made them choose not to device a safer experimental setup?

No, and there had already been an accident with this very core. https://en.wikipedia.org/wiki/Harry_K._Daghlian_Jr. Sadly, there was no good reason for this, just a young cocky guy. Not a bad man, and we've all made stupid choices, but his sadly was a bit historically significant.

I like the adage, "We all start with a bag of luck, filled, and a bag of experience, empty.

The trick is to fill your bag of experience up before your bag of luck runs out -- ie. when your bag of luck runs out, you die. Most people have a couple events in their life where they almost died -- of course we know we should have never made those choices -- but its easier said now that we have the experience knowing we got "lucky." :-)

I've never heard it put that way, but I've had this conversation with friends before, "Hey, remember when we almost died doing 'X'?" You're right, absolutely right.

A more modern version of a story like that often starts with "hold my beer ...".

> Slotin instructed one of his colleagues to lay radioactivity-detecting film badges around the area, which required the scientist to go dangerously close to the still overheated core.

Many managers and coworkers are so unthinking about their coworkers' health. Even without plutonium.

That part didn't make sense to me. Why does it stay more radioactive for a period of time after the accident? The pieces are separated - shouldn't it return to it's previous state? .I can understand it heating up (though can't you just cool it down mechanically?) but that's not really the same

Because lots if not most of the fission products are themselves very unstable, and will be decaying towards more stable isotopes in due course. I doubt this radioactivity was a fraction as dangerous as the criticality excursion he caused (and I'm sure he wasn't in a normal frame of mind after his screwup, which I'm sure he knew could eventually kill him), so it's a hopefully moderate at worst personal harm vs. unique opportunity to collect data trade off.

>> various items that were near the core—a bristle brush, an empty Coca-Cola bottle, a hammer, a measuring tape.

:groan:

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