The US dropped two atomic bombs on Japan in August of 1945, killing up to 250,000 people.
A third & fourth bomb (of the Fat Man type) were readied while Truman awaited Japan's response. The plutonium-gallium cores weighed 6.2-kilogram (14 lb) measuring 8.9 centimeters (3.5 in) in diameter.
Japan surrendered 15 August, so these bombs were never transported, but still managed to be lethal. Let's talk about the Demon Core.
Used for subcriticality experiments at Los Alamos, two criticality incidents with the third-shot core killed American scientists in 1945 and 1946.
These disassembled bomb cores were set up with neutron reflectors (tungsten carbide bricks) that allowed for subcritical research on bomb design.
So long as they weren't compressed, or fully enclosed, they generated high-energy neutrons at a steady rate, but didn't chain-react to explosion.
The first incident was August 21, 1945, when Harry Daghlian, working alone with only a security guard at a desk nearby, dropped a reflector brick directly on the core, producing a brief criticality event.
He died 25 days later of acute radiation poisoning. The guard died 33 yrs later of AML.
The second incident occurred May 1946 as Louis Slotin was showing Alvin C. Graves how to "tickle the dragon's tail" by propping beryllium reflector spheres with a screwdriver to moderate neutron reflection.
Slotin's hand slipped, there was a flash of light as the core reached SUPERcriticality.
Slotin received a dose of 1000 rad (10 Gy) died 9 days later of acute radiation poisoning, the others in the room, shielded by distance & Slotin's body, mostly died decades later, some of unrelated illness.
After this event, the core was melted down & used to manufacture other devices.
Two of the four people in this photo from the Trinity test died of acute radiation from the demon core.
Given the cowboy antics of the earliest atomic age, it's surprising more weren't killed. A reminder that every lab safety rule is written in blood.
I knew a guy who started a company to design & manufacture some of the optical instruments that were used to observe above-ground tests of atomic weapons (e.g. Bikini atoll). He had witnessed several of the tests. He died of leukemia, as did most of his co-workers who participated at the tests.
I had a prof who was over 90yo, survived like 4 different bouts of cancer, still walked to school every day even when it hit -20F or worse
I became unsurprised about the cancers after many lab stories in our Experimental Design class
Very much "do as I say, not as we did, we're lucky we all lived"
Bonus from another prof
On a team investigating adhesive used to attach heat shielding tiles to shuttles, tiles were falling off, team was stumped
Team finally watched a worker follow application instructions
Instructions did not say to remove tiles' protective film before applying the adhesive
It didn't end with the demon core nor was it restricted to nuclear materials. Beryllium for example has killed a number of people, including my father, who were involved in nuclear weapons work.
What I keep asking myself, given all this horrifying history, is how/why are nuclear submarines viable and if they are, why isn’t smaller scale/more modular nuclear power more of a thing?
And Navy nuke techs know what they are doing. So do the operators of large scale power plants.
Well, usually. Not great, not terrible, anyway.
The issue with small scale is that training and expertise often scales down as well, and that is not what you want when it comes to radiation safety.
Safety (nuclear and otherwise) is hardwired into all their training. (Source: I married a former Navy Nuke, and pelt him with questions for my books. He answers what he's allowed).
The USS Thresher and Scorpion are very much not forgotten by the US Navy.
I appreciate that Slotin yelled at everyone to come back into the room after they had fled, since "the danger has passed".
Getting everyone to mark exactly where they were standing with chalk marks on the ground was instrumental in learning from that criticality incident.
