Somewhere I have a document that talks about the August 21, 1945 accident and others. Luckily someone has posted the information online:
FATALITY FROM CRITICAL MASS EXPERIMENTS
Los Alamos, N. Mex., Aug. 21, 1945
During the process of making critical mass studies and measurements, an employee [Harry Daghlian] working in the laboratory at night alone (except for a guard seated 12 feet away) was stacking blocks of tamper material around a mass of fissionable material.
As the assembly neared a critical configuration, the employee was lifting one last piece of tamper material which was quite heavy. As this piece neared the setup, the instrument indicated that fission multiplication would be produced, and as the employee moved his hand to set the block at a distance from the pile, he dropped the block, which landed directly on top of the setup.
A "blue glow" was observed and the employee proceeded to disassemble the critical material and its tamper. In doing so, he added heavily to the radiation dosage to his hands and arms.
The employee received sufficient radiation dosage to result in injuries from which he died 28 days later.
The guard suffered no permanent injury. (See TID-5360, p. 2.)
Here's the Louis Slotin accident (which was depicted in the 1989 movie "Fat Man and Little Boy"):
INADVERTENT SUPERCRITICALITY RESULTS IN DEATH
Los Alamos, N. Mex., May 21, 1946
A senior scientist [Louis Slotin] was demonstrating the technique of critical assembly and associated studies and measurements to another scientist. The particular technique employed in the demonstration was to bring a hollow hemisphere of beryllium around a mass of fissionable material which was resting in a similar lower hollow hemisphere.
The system was checked with two one-inch spacers between the upper hemisphere and the lower shell which contained the fissionable material; the system was subcritical at this time.
Then the spacers were removed so that one edge of the upper hemisphere rested on the lower shell while the other edge of the upper hemisphere was supported by a screwdriver. This latter edge was permitted to approach the lower shell slowly. While one hand held the screwdriver, the other hand was holding the upper shell with the thumb placed in an opening at the polar point.
At that time, the screwdriver apparently slipped and the upper shell fell into position around the fissionable material. Of the eight people in the room, two were directly engaged in the work leading to this incident.
The "blue glow" was observed, a heat wave felt, and immediately the top shell was slipped off and everyone left the room. The scientist who was demonstrating the experiment received sufficient dosage to result in injuries from which he died nine days later. The scientist assisting received sufficient radiation dosage to cause serious injuries and some permanent partial disability.
The other six employees in the room suffered no permanent injury. (See TID-5360, p. 4.)
But the one that always horrified me was this one:
FATAL INJURY ACCOMPANIES CRITICALITY ACCIDENT
Los Alamos, N. Mex., Dec. 30, 1958
The chemical operator introduced what was believed to be a dilute plutonium solution from one tank into another known to contain more plutonium in emulsion. Solids containing plutonium were probably washed from the bottom of the first tank with nitric acid and the resultant mixture of nitric acid and plutonium-bearing solids was added to the tank containing the emulsion. A criticality excursion occurred immediately after starting the motor to a propeller type stirrer at the bottom of the second tank.
The operator fell from the low stepladder on which he was standing and stumbled out of the door into the snow. A second chemical operator in an adjoining room had seen a flash, which probably resulted from a short circuit when the motor to the stirrer started, and went to the man's assistance. The accident victim mumbled he felt as though he was burning up. Because of this, it was assumed that there had been a chemical accident with a probable acid or plutonium exposure. There was no realization that a criticality accident had occurred for a number of minutes. The quantity of plutonium which actually was present in the tank was about ten times more than was supposed to be there at any time during the procedure.
The employee died 35 hours later from the effects of a radiation exposure with the whole-body dose calculated to be 12,000 rem +.
Two other employees received radiation exposures of 134 and 53 rem, respectively. Property damage was negligible. (See TID-5360, Suppl 2, p. 30; USAEC Serious Accidents Issue #143, 1-22-59.)
I guess if I were ever to be the victim of Acute Radiation Syndrome I would want to go like the last guy. Not hanging around for a month or so of great pain and heroic lifesaving attempts and weeping relatives, but BANG and the next day you're dead. The link to the document is here:
http://www.ciar.org/~ttk/hew/accident/critical.htm
Yes, I read about that incident. Imagine turning on a stirrer and all hell breaks loose. I don't understand why they opine that maybe the "flash" happened because of a short-circuit in the stirrer motor. Daghlian and Slotin got much smaller doses and in those cases witnesses described seeing a "blue flash" of Cherenkov radiation. It would seem to me that there would have been a hell of a blue flash in this case if the guy got 12K rad.
Maybe the radiation blast was so intense that it broke down the insulation inside the motor and that shorted it out.
For me the most chilling story is the one about the Israeli guy who went into a radiation sterilizer to clear a product jam while the cobalt-60 source was exposed (the product jam hid it from visibility, but didn't hid him from the radiation).
Google the phrase Soreq JS6500 to find it. The guy was exposed between one and two minutes (he wasn't sure how long) at 1000 rad/minute. He lasted 36 days, but was given heroic levels of treatment including a bone marrow transplant from his brother.
(steely)