1. Accidents in the Manhattan project During the Manhattan project there were three fatal accidents that caused the death of four people for high exposure to nuclear radiation. These people were brilliant engineers chemists and scientists who because of poor security measures ended prematurely their lives and their contribution to the development of the first atomic bomb. These are their names: Peter Newport Bragg Jr. 1920 – 1944 Douglas Paul Meigs 1918 – 1944 Harry K. Daghlian, Jr. 1921 – 1945 Louis P. Slotin 1910 - 1946

2. The Philadelphia Explosion On September 2, 1944, three men entered the transfer room of the liquid thermal diffusion semi-works at the Philadelphia Navy Yard to repair a clogged tube. The tube they were working on consisted of two concentric pipes with liquid uranium hexafluoride circulating in the space between them; the innermost pipe contained high- pressure steam. Kneeling on the floor with a Bunsen burner, Bragg and Meigs worked to free the clogged tube. Without warning, at 1:20 PM, there was a terrific explosion. As the tube shattered, the liquid uranium hexafluoride combined with the escaping steam and showered the two engineers with hydrofluoric acid, one of the most corrosive agents known. Within minutes, both Peter Bragg and Douglas Meigs, with 3rd degree burns over their entire bodies. Due to the extreme secrecy surrounding the Manhattan Project in general and the experimental facility at the Philadelphia Navy Yard in particular, an immediate veil was drawn down over the incident by the highest authority available: General Leslie Groves. Due to the extreme secrecy surrounding the incident, even the Philadelphia coroner was not made aware of the actual causes of death.

3. The Philadelphia Record Philadelphia, Pa. September 3, 1944 SIDE OF BUILDING RIPPED OUT; FIRE EXTINGUISHED - Two specialists were killed and nine other men injured late yesterday afternoon when an explosion, followed by fire, ripped out the side of a building at the Navy Yard. Gas was released, burning the lungs of some of the men. They were given first aid at the scene and then sent to the Naval Hospital. At least one is in "a very critical condition," the Navy announced. Two other men, Navy Yard firemen, collapsed while fighting the blaze. Their condition is not serious. The two men who died following arrival at the Naval Hospital were: Douglas P. Meigs, 26, Tacoma Park, Md., an employee of the H. K. Ferguson Company of Cleveland. Peter N. Bragg Jr., 24, Fayetteville, Ark., a Navy chemical engineer. The injured included five U. S. Army first class privates "9 Are Injured; Blast Heard in Wide Area"

4. Peter Newport Bragg Jr. A brilliant chemical engineer, he volunteered for a dangerous assignment while employed by the U. S. Navy Research Laboratory's "pilot-plant" at the Philadelphia Navy Yard. His work was crucial to the development of the first atomic bomb, and in his own way, his contribution helped bring about an early end to World War II.

5. Douglas Paul Meigs A brilliant chemical engineer too, he volunteered for a dangerous assignment while employed by the H. K. Ferguson Company of Cleveland, OH.

6. The dragon bites In August of 1945 and again, in May 1946, two Los Alamos scientists were exposed to lethal doses of radiation while performing experiments to determine critical mass. These experiments, performed at the Omega Site, were commonly referred to as "Tickling the Tail of the Dragon". Although several months apart, both accidents occurred on a Tuesday and both on the 21st of the month...and, both men died in the same hospital room at the U.S. Engineers Hospital at Los Alamos.

7. The first dragon bites On 21 August, 1945, Daghlian was involved with a series of experiments at Omega Site. As he disassembled the afternoon experiment, Daghlian began planning the next criticality test and, after making some final remarks in his notebook, he decided to construct the next assembly on a 10-5/8 inch square base. After dinner, Daghlian began thinking about returning to Omega Site that evening to test the third assembly, rather than the following morning as originally planned. He was well aware that this was against "official" safety regulations on two counts, performing a potentially hazardous experiment alone after-hours Photo of the critical assembly after the accident and dismantling by Daghlian. A nickel-plated sphere of 49 metal is shown supported by a WC (tungsten carbide) cradle and surrounded by a base of WC bricks.

8. Entering the laboratory, he found Private Robert J. Hemmerly, a Special Engineer Detachment (SED) guard, seated at a desk and reading a newspaper. Hemmerly looked up apprehensively at a somewhat anxious Daghlian, who tried to mask his nervousness by walking directly to the assembly bench. Daghlian immediately set about removing the 49 metal sphere from the vault and constructing the planned assembly. As he attempted to place another brick over the center of the assembly with his left hand, the "clicks" alerted him to the possibility that this addition would be supercritical, and he immediately started withdrawing his left hand when the brick fell from his grasp into the center of the assembly. Reacting instinctively, he pushed the brick from the assembly with his right hand, which developed a tingling sensation as it became enveloped in the blue glow surrounding the sphere.

9. At the time of the accident, Pvt. Hemmerly of Columbus, OH was 29 years old, married, and the father of two children. On admission to the hospital, he was confined to bed for two days of observation. Ten months following exposure, Hemmerly's physical condition was unchanged and completely normal, and he had no subjective complaints In contrast, Daghlian's total-body radiation exposure was estimated to be 480 roentgens of soft x-rays and 110 roentgens of gamma rays, with additional complications arising from the non-uniform distribution of radiation exposure, particularly to the upper body and, especially, to the left hand. On the tenth day after exposure, Daghlian experienced nausea and abdominal pain after eating. During the course of his illness, Daghlian's medical treatment was predicated on alleviating his symptoms rather than attempting to halt or reverse the radiation-induced injuries Several days prior to his death, he became irrational and slipped into a coma on the final day of his life. Daghlian died at 4:30 PM on Saturday, 15 September, 1945; he had survived almost 26 days after the accident at Omega Daghlian's right hand nine days after the accident.

10. Information provided in the press release from Los Alamos led the New York Times to report that Daghlian had died from "chemical burns," rather than from the results of radiation-induced injuries. This omission, in effect, rendered Daghlian's service and sacrifice a relatively obscure footnote to the history of Project Y. Harry K. Daghlian, Jr

11. The dragon bites… Again It happened in an instant. A sudden blue glow momentarily enveloped the room before evaporating. In that moment, as the Geiger counter clicked wildly, scientist Louis Slotin knew that he had received a lethal dose of gama and neutron radiation from the core of the plutonium bomb he was testing. It was 3:20 P.M. on Tuesday, 21 May 1946, at the secret Omega Site Laboratory. With his left thumb wedged into a cavity in the top element, Slotin had moved the top half of the sphere closer to the stationary lower portion, a micro-inch at a time. In his right hand was a screwdriver, which was being used to keep the two spheres from touching. Then, in that fatal moment, the screwdriver slipped. The halves of the sphere touched and the plutonium went supercritical. The chain reaction was stopped when Slotin knocked the spheres apart, but deadly gamma and neutron radiation had flashed into the room in a blue blaze caused by the instantaneous ionization of the lab's air particles. Louis Slotin had been exposed to almost 1,000 rads of radiation, far more than a lethal dose

12. Slotin had been instructing a colleague, Alvin C. Graves, who was to replace him at the Omega Site. Also present was S. Allan Kline, a 26-year-old graduate of the University of Chicago, who had been called over to observe the procedure. Five other colleagues were close by as Slotin, a Canadian physicist from Winnipeg who had been part of the team that created the atomic bomb, performed the action that would bring into close proximity the two halves of a beryllium-coated sphere and convert the plutonium to a critical state. There is some small variation in detail about what happened after Slotin knocked apart the two beryllium spheres, while using his body as a shield to protect the other men. The sketch was used by doctors to determine the amount of radiation to which each person had been exposed.

13. After arriving at the Los Alamos hospital Slotin told Alvin Graves: "I'm sorry I got you into this. I'm afraid I have less than a 50 per cent chance of living. I hope you have better than that." Many volunteers were ready to donate blood for the transfusions doctors deemed necessary. Sadly, all efforts to save Slotin were futile. He died on 30 May after an agonizing sequence of radiation-induced traumas including severe diarrhea and diminished output of urine, swollen hands, erythema (redness) on his body, massive blisters on hands and forearms, paralysis of intestinal activity, gangrene and a total disintegration of bodily functions. It was a simple case of death from radiation, similar to what American scientists and medical personnel saw in Japan among A-bomb victims. Dr. Louis Slotin at work, date and location unknown.

14. It had been ominously augured by a very similar tragedy six months earlier. Harry Daghlian, Slotin's friend and laboratory assistant, had fallen victim to "the invisible killer". Deeply saddened by the mishap, Slotin spent many hours at his assistant's bedside during the month it took Daghlian to die. Thomas Brock quotes from a June 1946 letter from Emily Morrison, Philip Morrison's wife, to a friend. It reveals the "series of strange coincidences" involved in both mishaps: "Both Louis' and Harry Daghlian's accidents occurred on Tuesday the 21st; both used the same piece of material; and both died in the same room in the hospital." After the 24-year-old Daghlian's death, Nobel Laureate Enrico Fermi warned Slotin that he wouldn't last a year - "if you keep doing that experiment." Following the Daghlian accident two tiny spacers were developed to prevent the beryllium spheres from closing completely together. It was hoped that this would prevent similar incidents. But Slotin preferred a hands-on approach to experimentation. Slotin's death ended all hands-on critical assembly work at Los Alamos. We immediately started work on a remote control system with the critical assembly equipment and the operating crew separated by roughly a quarter mile. We had no more criticality deaths or injuries.

16. Louis P. Slotin