By 9:55 Daghlian had built his five-layer brick house around the bomb core, holding the brick that would seal the top in his left hand. Slowly he lowered it toward the pile, and the neutron counters started chattering madly. He had passed the critical line, barely, but the sudden radiation was startling. His left arm jerked upward to get the brick away from the pile. It slipped out of his hand.
Hemmerly was still sitting with his back to the assembly table, but he heard the rash of counts over the loudspeaker and then the clunk and the WC brick fell across the top of the plutonium ball, centered perfectly. The neutron detectors overloaded and the speakers went quiet as the wall in front of him lit up with a blue flash, and he twisted around.
Daghlian had caused a problem, and every instinct told him to immediately erase the problem. With his right hand he knocked the WC brick off the top of the assembly, glowing a pretty blue, and he noticed the tingling sensation of direct neuron excitation. He then stood there, arms limp by his sides, coming to grips with what had just happened.[44] He decided to dismantle the pile of bricks, and he calmly told Hemmerly what had occurred. Joan Hinton, a graduate student, happened to have just arrived at the Omega Site, and she drove the stunned scientist to the Los Alamos hospital as Hemmerly alerted Sgt. Starmer. Starmer was in the Omega Site office, which was separated from the 49 Room by a five-foot-thick shielding wall.
Daghlian’s right hand had endured a high dose of x-rays, gamma rays, and high-speed neutrons. There was no direct way to record the dose to his palm, used to brush aside the WC brick, but it was probably 20,000 to 40,000 rem. His left hand took a hit of 5,000 to 15,000 rem as the brick hit the pile. His body absorbed about 590 rem.[45]
The first symptom of Daghlian’s radiation exposure observed at the hospital was the swelling and numbness in his right hand. Unrelenting nausea started 90 minutes after the accident, and continued for two days with a break only for prolonged hiccups. After 36 hours, a small blister appeared on his ring finger. Shortly after, the circulatory system in his hand collapsed and it turned blue, beginning with the nail beds. The blistering spread to the palm and then the back of the hand, and the hand essentially died. He was given opiates and ice packs in an attempt to control the pain.
After two days, he was feeling better and he was hungry. His arms, face, and body were turning red and skin was starting to come off, but he ate well and seemed to be improving. On the tenth day, the severe nausea returned, and he was no longer able to keep anything down. He started losing weight. He was given a blood transfusion, large doses of penicillin, vitamin B1, and quinidine sulfate. No treatment was reversing the condition. After 25 days, he slipped into a coma. He died at 4:30 P.M. on Saturday, September 15, 1945. His obituary in the New York Times said that he had perished from chemical burns. Harry Daghlian was the first person to die accidentally of acute radiation poisoning. It was history’s first mini-disaster involving nuclear fission out of control. The bomb core, not in its assigned role, had inadvertently become an unshielded nuclear reactor, suddenly achieving supercriticality and with no automatic shutdown system in place. There was nothing that could have been done medically to save his life.
The other victim, Private Hemmerly, had been exposed to the same radiation burst, but from a distance of 12 feet. He was confined to a bed for two days, with his only complaint that he felt tired. His blood samples showed increased leukocytes, but this condition was only temporary, and he was released after three days and returned to active duty. He went on to father two more children, and he died at the age of 62, showing no medical evidence that he had ever been exposed to a naked nuclear reactor. The difference between him and Daghlian was apparently the distance to the radiation source. In informed retrospect, if Daghlian had recoiled, jumping back from the assembly table when he dropped the brick instead of bending over to brush it off the pile, he would have survived. If he had been standing on the south side of the table instead of the north side, as was the case with Heisenberg and Döpel, he could have been out the door in three desperate bounds, with Hemmerly right behind him.
But, what would have happened to the supercritical plutonium ball? After a few seconds of power increase, the immediate temperature rise would have shut it down as the sphere expanded in the heat. The supercritical condition in a metal reactor of this size is so sensitive to perturbation, just a slight increase in the distances among plutonium nuclei is sufficient to stop the fissions. It would have then sat there with the heat diffusing slowly to the surface of the ball and radiating out into the room. As soon as it had reached room temperature, it would again become supercritical, and the cycle would start again, hosing the room once more with radiation.[46] After a few cycles, the movable WC bricks would be nudged to the sides by the expanding ball enough to no longer encourage another supercritical excursion, and the assembly would be stable but dangerous. A technician would enter the room behind a lead shield and dismantle the pile using a 20-foot metal pole, and Daghlian would have never been allowed again in the 49 Room.
This shocking event should have been a strong lesson learned, with measures implemented immediately to prevent its further occurrence. But, it wasn’t. Louis Alexander Slotin, an expert at assembling bomb-core experiments, was one of three investigators who submitted the accident report on August 26, 1945, five days after the Daghlian incident.
Slotin was born in 1910 to Jewish refugees who had fled the pogroms of Russia to make a life in Manitoba, Canada. He grew up on the north end of Winnipeg in a tight cluster of Eastern European immigrants, and he proved to be academically exceptional. He entered the University of Manitoba at age 16, earning a Bachelor of Science degree in 1932 and a Master of Science a year later, both in geology. Further study at King’s College London led to a Ph.D. in chemistry in 1936 and a wealth of dubious exploits. Later in life he would claim to have test-flown the first jet plane developed in England, despite lacking a pilot’s license. He captivated those listening with tales of having volunteered for service in the Spanish Civil War just for the thrill of it, although there was some confusion as to which side he was on.[47] At King’s he won the college’s amateur bantamweight boxing championship. His first job out of school was testing rechargeable batteries for the Great Southern Railways in Dublin, Ireland.
Back home in 1937, Slotin was turned down for a position with Canada’s National Research Council. He wangled a job as a research associate at the University of Chicago, where he worked on a cyclotron under construction in the Old Power Plant building. The pay was pitiful, but with help from his father to buy food he stayed on for a few years, using the new particle accelerator to make carbon isotopes for biological studies. It was claimed that he was present at Enrico “The Pope” Fermi’s CP-1 reactor startup in 1942, but nobody remembered him being there. He was caught in the sweep of the Manhattan Project draft and wound up at the Clinton Works in Oak Ridge.
At Oak Ridge he gained a reputation as someone who would step over the safety line and take chances that should not be taken. One Friday afternoon, young Louis wanted the X-10 graphite reactor shut down so that he could make adjustments to his experiment at the bottom of the fuel pool. It was a tank of water under the floor at the back of the reactor where hot, very radioactive fuel was dumped to cool off. The head of health physics, Karl Z. Morgan, nixed the idea. The pile could not possibly be shut down. It was being used as a pilot plant for the plutonium production reactors being built at Hanford, and the thing had to run 24/7, balls to the wall. Every few days, new fuel was pushed into the front face of the reactor, and the burned-up fuel would fall into the pool. The bottom had to be heavily contaminated by now.
44
A characteristic that all criticality accidents seem to have in common is the blue flash. It is caused by the sudden blast of radiation from the uncontrolled chain reaction ionizing nitrogen gas in the air and causing it to glow a characteristic color. In this first case, the glow was about two inches deep around the box made of WC bricks.
45
Roentgen Equivalent Man. The rem is an obsolete measure of radiation dose, taking into account the unique sensitivities of the average human body. Doses in the range of 1,000 rem are usually fatal. The current measure of dose is the sievert. To convert rem to sieverts, divide the value in rems by 100.
46
The “supercritical” condition is necessary for this to be a disaster. Any reactor can be exactly critical, conducting self-sustaining fission, while generating no detectable power. The only way to bring an operating reactor up to a useful power-level is to temporarily add some reactivity, making it slightly supercritical. When the power level is achieved, the reactor is leveled off at exactly critical. To lower the power level, the reactor is rendered slightly subcritical on a temporary basis.
47
Slotin’s brother, Sam, in a later interview revealed that Louis had gone on a short walking tour in northern Spain and had participated in the revolution only in spirit.